Tetraethyl Lead: The Solution To One, And Cause Of Many New Problems

From the 1920s until the 1970s, most gasoline cars in the USA were using fuel that had lead mixed into it. The reason for this was to reduce the engine knocking effect from abnormal combustion in internal combustion engines of the time. While lead — in the form of tetraethyllead — was effective at this, even the 1920s saw both the existence of alternative antiknock agents and an uncomfortable awareness of the health implications of lead exposure.

We’ll look at what drove the adoption of tetraethyllead, and why it was phased out once the environmental and health-related issues came into focus. But what about its antiknock effects? We’ll also be looking at the alternative antiknock agents that took its place and how this engine knocking issue is handled these days.

It’s a Matter of Octane

In an internal combustion engine (ICE), ideally the air-fuel mixture that gets injected into a cylinder will ignite at the perfect moment where the flame front will travel outwards from the point of ignition, with every bit of the air-fuel mixture burning up fully. This will allow for maximum use of the energy in the fuel mixture, while causing a clean stroke of the piston.

In reality, however, pockets of this fuel-air mixture will ignite before the flame front reaches them. These so-called ‘cool flames’ occur because of the compression by the piston combined with slight unevenness in the mixture, causing additional pressure waves in the cylinder. This raises the cylinder pressure and causes the typical metallic pinging noise that is indicative of engine knocking. Depending on how many of these pockets ignite outside of the spark plug’s flame front, the result may be increased wear on components, or even their outright destruction.

Hereby the octane rating of the fuel is crucial, as it essentially determines at which compression level the fuel will ignite (without spark). High octane fuels thus do burn less easily, but allow for far higher levels of compression, which effectively produces more power. In contrast, diesel engines require lower octane fuels, as they only compress air, with the fuel being injected at the end of the compression cycle, with the heat from the compressed air igniting the fuel.

Time to Knock It Off

There are fortunately a number of ways to prevent this premature ignition effect. These include:

  • Using a fuel with a higher octane rating.
  • Adding more fuel to the air-fuel mixture.
  • Reducing the compression level in the cylinder.
  • Reducing the load on the engine.

You can choose the first point by using a so-called antiknock agent, a chemical that raises the octane rating of the fuel by raising the temperature and pressure at which auto-ignition occurs. Tetraethyl lead (TEL) is one example of such an agent. Its chemical formula is (CH3CH2)4Pb.

Inside the engine’s cylinders, the function of TEL is to quench the spontaneous ignitions that occur outside of the flame front by dealing with the pyrolized radicals that would otherwise sustain the chain reaction of the cool flame. Here the lead is the actual reactive agent, while the rest of the TEL serves to allow it to dissolve into gasoline (courtesy of its alkyl groups).

As the TEL is burned, it produces carbon dioxide, water and lead:

(CH3CH2)4Pb + 13 O2 → 8 CO2 + 10 H2O + Pb

The lead can further react with oxygen to form lead(II) oxide:

2 Pb + O2 → 2 PbO

Left alone, the lead and lead(II) oxide would accumulate inside the engine and destroy it. To prevent this, lead-scavengers such as 1,2-dibromoethane and 1,2-dichloroethane are added to form lead(II) bromide and lead(II) chloride respectively (unfortunately neither are as pretty as lead(II) iodide). These compounds are easily removed from the engine during normal operation, from where they’d be released into the environment.

The Competition

In addition to lead, two other substances were known to increase the octane rating of gasoline fuel: ethanol (C2H6O) and benzene (C6H6). For ethanol this octane rating raising property is due to ethanol being suitable as a complete (albeit more expensive) replacement for gasoline fuel. As ethanol has by default a higher octane rating than most gasoline fuels, mixing a percentage of ethanol into gasoline fuel causes the latter to have a higher octane, which achieves the desired anti-knocking effect.

When adding lead to gasoline was a plus. (Plazak, CC-BY-3.0)

Benzene is a hydrocarbon which appears naturally in crude oil. It’s present in gasoline as a result, where it’s also responsible for the characteristic sweet smell around gasoline refueling stations. Although now usually kept at less than 1% in gasoline due to the carcinogenic properties of benzene, before TEL’s introduction in the 1920s as a fuel additive, benzene was regarded as a good antiknock agent as it too raised the octane rating. By the 1950s TEL had virtually replaced benzene as antiknock agent.

Ethanol can be produced from oil (ethylene), as well as from biomass (sugar cane, corn, etc.). It is however a fuel type that has only seen widespread popularity since the 1970s. TEL had the benefit over ethanol as an antiknock agent that only a small amount would be needed to have the same effect, yet at similar cost. TEL however also had the additional benefit that its use as fuel-additive could be patented.

TEL Fallout

Ultimately history shows us that TEL would prevail over benzene and ethanol, with ethanol only making a resurgence in the 1970s during the phase-out of TEL. As information uncovered over the past decades shows, the reason for this was a deliberate strategy by the companies behind the Ethyl partnership (General Motors, ESSO and DuPont) to bury the science about the well-known harmful effects of lead, the expected blood serum lead levels from adding TEL to gasoline and the expected effects on the environment.

As this 2005 paper by William Kovarik (PDF) summarizes, the use of ethanol as an antiknock agent was commonplace by the time that TEL was introduced, but over the decades, the misinformation campaign by Ethyl was so effective that people came to believe that TEL was the only antiknock agent available. In the end it would take fifty years of research, as well as scientific, court and regulatory challenges to produce evidence about the harmful effects of TEL that were so damning that leaded gasoline was phased out in the 1970s in the US, though not without Ethyl first suing the Environmental Protection Agency (EPA).

Among one of the effects noted by researchers of the effects of increased lead levels in blood serum was that of a sharp negative effect on the developing brain, leading to a lower IQ, poor impulse control and troubles at school. Later studies introduced the lead-crime hypothesis, which links the rise in violent crime since the 1930s and the sharp drop-off in the early 1990s with the exposure of children to high blood serum lead levels, which would have impaired brain development.

Although the Ethyl corporation still exists today, the use of TEL in gasoline has been essentially reduced to zero, aside from use in aviation fuel, antique cars, and so on. As the use of TEL is incompatible with catalytic converters due to lead being a catalyst poison, the requirement of adding a catalytic converter to new cars in the late 1970s US made the demise of TEL for cars a certainty. Europe, Asian nations and so on also phased out TEL until today only one plant in the world still (legally) produces leaded gasoline.

Antiknock Strategies Today

Even though modern ICEs have hardened components that can withstand engine knocking without damage, and the mixing of ethanol into the gasoline fuel is becoming ever more commonplace, other antiknock agents are still around, with methylcyclopentadienyl manganese tricarbonyl (MMT, (C5H4CH3)Mn(CO)3) having been used for years in a number of countries.

Ferrocene (Fe(C5H5)2) is also used as a fuel additive, used as an alternative to TEL, such as for use in antique cars. Increasing the amount of 2,2,4-trimethylpentane (iso-octane, also a petroleum product) in gasoline serves to reduce the knocking, as was originally discovered by Graham Edgar in 1926. Iso-octane forms the 100 point on the octane rating scale.

In addition to fuel additives, modern digitally controlled gasoline engines have built-in mechanisms that detect and control engine knocking, by adjusting the ignition timing and pressure. This allows for the engine to automatically adjust itself to fuels with different octane ratings. This of course comes with its own set of challenges, as for example this 2017 paper by Peyton Jones et al. titled “Stochastic Simulation and Performance Analysis of Classical Knock Control Algorithms” details.

Just A Historical Footnote

It’s interesting to consider these revelations and new innovations in light of the transition of the car industry from the internal combustion engine to electric motors, which do not have any of these issues. Free from the stigma of leaded gasoline and its combustion products, it will be interesting to see how we will regard this chapter in human history fifty years from now.

By then not having regenerative braking would probably seem beyond quaint, as would be the ritual of weekly (or daily) refueling or recharging. Maybe the issue of fine particulate dust from tires and brake disks will have become the next environmental issue.

[Main image source: Tetraethyl Lead by David Brodbeck CC-BY 2.0]

101 thoughts on “Tetraethyl Lead: The Solution To One, And Cause Of Many New Problems

    1. He also came up with a clever hack for removing very fine metallic particles in his eye of low melting point that sprayed out from a fusible boiler pressure relief plug. The particles were too fine and large in number for easy manual removal… the solution… he put liquid mercury in an eye cup and used it to dissolve the metal particles from the eye.

      He also managed to give himself tellurium poisoning at one point while testing fuel additives. He smelt so badly of garlic, which is characteristic of tellurium poisoning, it is reported that he was not allowed on the tram home.

    2. Big Wiki says he was working with Charles Kettering, the inventor of the first electric starter. They were apparently situated in Dayton, OH from whence comes the D in Delco which of course later became part of GM. According to the sticker, my Trek came from (or was serviced at) Kettering Bike Shop in Dayton, which is irrelevant but makes it harder to forget.

      This was an excellent article about the whole lead fiasco, having made the rounds at Hacker News a few times: https://www.mentalfloss.com/article/94569/clair-patterson-scientist-who-determined-age-earth-and-then-saved-it

  1. The US was one of the first nations to restrict and outlaw the use of leaded gasoline. You could buy leaded petrol in the UK for many years after it was outlawed in the US. BTW it is illegal to run leaded fuel in a street car and even most race fuels today are unleaded.
    As to octane boasters you left out methanol.
    As to modern car engines being hardened to with stand knocking that is simply not true. The electronic controls as stated handle preventing damage. Modern engines do have hardened valve seats to deal with the lack of lead. Another major improvement is with modern combustion chamber design. It was discovered that turbulence was good in the combustion chamber modern combustion chambers are designed to generate that during the compression stroke which is why a modern engine can run at a much higher compression ratio than an older engine using the same fuel.

    1. There’s a gas station on the MA/NH border called Haffner’s. Last time I was there you could get 110 leaded right at the pump. Used to fill our bikes with it when we would go for a ride in that area just because the race fuel smelled so good

          1. Most importantly, it’ll damage your health and the environment. Lead is highly toxic at any level. It’s a filthy crime that leaded gasoline/paint/ammunition/plumbing, etc. was ever allowed to be unleashed on this planet. They knew it was deadly, but used it anyway. Fortunes should have been stripped and people put in jail.

          2. > Lead is highly toxic at any level.

            If you believe in homeopathy.

            The level of lead in normal soil is 10 to 50 mg/kg. Contamination by leaded gasoline around urban environments raises that to 150 mg and up to 10,000 mg in the most contaminated places, like around a house painted with lead paint where the paint has flaked off and fallen to the ground. Less than 150 mg /kg is considered “not contaminated”.

            Point is, there is an appreciable amount of lead in the environment anyways and it’s not “highly toxic”. It’s actually pretty insoluble because it tends to bind chemically to minerals, like lead phosphate. It’s the dose that makes the poison in this case as well.

          3. @luke three times the level of lead is A LOT. If you ate three times the food, drank three times the alcohol or coffee, etc, I suspect you would feel very much different.

            Besides, fresh lead from gas, ammo, or whatever might not be chemically the same as ancient lead in soil, but I’m not a chemist. I know methylmercury I a lot different from elemental, so I would be surprised if TEL had some extra bad properties, or if fine dust from lead ammo did too.

          4. >”three times the level of lead is A LOT”

            Not really. You’re still within the same order of magnitude, and probably at the upper limits of natural variation. But the point is, there’s lots of nasties out there that we’re simply evolved to deal with. There is a “safe” level of lead exposure by the fact that it is tolerated to an extent – whenever you hear people saying “unsafe at any level of exposure”, they’re talking out of their asses.

          5. > fresh lead from gas, ammo, or whatever might not be chemically the same

            Fresh lead from gasoline, ammo, is very harmful because it’s mostly bound in organic compounds that are fat soluble, and enter the bloodstream easily. Once the lead is on the ground, it tends to form inorganic compounds which are far less likely to be absorbed.

          6. @Luke

            > You’re still within the same order of magnitude, and probably at the upper limits of natural
            > variation.
            > But the point is, there’s lots of nasties out there that we’re simply evolved to deal with.

            But lead isn’t one of them. There is no ‘natural’ background level of lead contamination, and thus we’re not evolved to deal with it.

            > There is a “safe” level of lead exposure by the fact that it is tolerated to an extent

            Lead is a cumulative toxin, so it’s only ‘tolerated’ while our cumulative lifetime exposure remains low enough that the effects are minimal.

      1. There’s a gas station in Sunol California (northeast of Silicon Valley) that has racing gas in various high octanes. I don’t think leaded 110 octane is still available, but there are still some fairly high octane high priced fuels. (I’m assuming California or maybe the Feds tightened the lead rules further a few years back, but maybe it was just declining market, plus the real way to go fast these days is a Tesla.)
        I’d be surprised if there aren’t high-octane stations near Sears Point and Laguna Seca as well.

      1. AFAIK leaded fuel is only for a majority of piston-engined aircraft that runs on avgas (so small general-aviation aircraft or antiques). Other piston-engined aircraft use engine designs derived from diesel engines and so burn kerosene or jet fuel, the latter also being used on jets (including commercial airliners).

        As far as I can tell, neither kerosene nor jet fuel contain lead.

        1. Lead is still used in aviation fuels because alcohols are not suitable in carbureated gasoline engines that have to function reliably at high altitudes and cold temperatures. Alcohols have an affinity for water. They will absorb it from the air. They also have a high latent heat of evaporation and produce a cooling effect when vaporized. Those 2 factors can result in a carbureator icing up.

      2. Lead is toxic at ANY level. Every exposure is harmful. It impacts IQ, cognition, impulse control, heart, lung, kidney, and other functions. Lead moves to the bones within about 36 days of exposure, rendering the lead blood test useless for lower-level, chronic exposure. You can have bones & vital organs riddled with lead, yet have “normal” blood test results, so you will not receive treatment.

        1. Lead is toxic, in organic form, yes, in metallic form, not so much. Pure lead air rifle pellets in your mouth, hardly worth mentioning, a drop of organic lead salt on the other hand, that can kill you softly, with it´s song.

          1. Yeah, though like most toxicology or reference data… kind of like lab testing… there is a generic method and reporting scheme that is generalized.

            Like the Ranitidine with the N-nitrosodimethylamine (NDMA) issue and others issues associated with toxicology… maybe if you’ve seen, based on diet… some people may have more an issue that others.

        2. Organic lead, just like organic mercury, is highly toxic as already stated by other. However, when TEL burns in an engine, it turns into inorganic salts like lead chloride or lead Bromide. This is even mentioned in the article. The small amount you might be exposed to is largely insignificant. There’s been a lot scary talk about leaded gasoline, but it’s mostly uninformed fearmongering by people who know nothing about chemistry. The real truth is that lead was not removed from gasoline because of health concerns. It was the catalytic converter that killed leaded gasoline. Lead will destroy a catalytic convert by depositing itself onto of the catalyst material and render it useless. when unleaded gas was introduced they made the nozzle on the pump slightly smaller and cars that required unleaded fuel, because of they had catalytic convertors, had a smaller opening in the fuel port to prevent you from inserting the nozzle of leaded gas pump.

          It should also be noted that many of the alternatives to lead are not healthy chemicals either. And some can produce nasty by products that aren’t good to breathe. For example alcohols can sometimes, under certain conditions produce aldehydes. Those have a nasty habit of causing cancer. Google “aldehydes from alcohol in gasoline” and read for yourself.

        3. Let’s all take a knee and give thanks that ‘Big Bad’ TEL was there for us in WWII, because it allowed the 145/160 avgas that allowed the super high boost pressures in our fighter planes to give us an edge in performance over the Axis. : )

    2. This comment is spot on. Lead was also used to partially coat exhaust valves to reduce wear, and modern engines have hardened components to deal with that issue, but it’s just as easy to break a modern engine if it knocks as it is with a 1960s design.

      There are a lot of octane boosters out there that can work, although not all of them make sense as a commercial product. There was one time at the PRI trade show that we happened to need some 93 octane gas, at least, for a turbo Miata dyno demonstration, and couldn’t find anything better than 91 octane. (Note for non-US readers – US octane measurements are on a slightly different scale from the rest of the world and are a few points lower.) We ended up going to a paint store and dumping several cans of toluene in the tank, and getting a suitably knock-free demonstration.

    1. C2H6O is a perfectly acceptable description of dimethyl ether. IUPAC standards are to list the atoms in alphabetic order with the number of each following the atom. If you want to convey structural information, sure, C2H5OH is nice, or CH3OCH3 for dimethyl ether, but nobody tries to follow this kind of nomenclature for the structural formula for penicillin or heroin or testosterone. If you’re going to convey structural information, use the IUPAC name, which is unambiguous.

  2. Using colder range spark plugs will also help prevent pinging. The Ford Vulcan V6 is basically made to handle preignition, but I couldn’t stand hearing it and went to colder plugs!
    Alot of people don’t think about where all that brake and tire dust goes and most of it is smaller than PM2.5 which can get deep into your lungs. Some brakes still contain asbestos and thats one reason its recommended to wet the brake dust down with water when changing brake pads as well as ppe! Mention the dusts to anyone who touts EV as emission free and they lose their minds. I wonder how they are going to tackle those emissions in cities that are banning ICE cars in the future.

    1. I’ve never heard of anyone using water to wet down brakes when changing them – that’s what brake cleaner is for.

      EVs leave a whole lot less brake dust around because of the regenerative braking. Still better than ICE cars by a long shot.

      1. Yep. Sure EVs produce some brake dust and they sure produce plenty of tire dust (possibly more due to their higher mass from the batteries), but the regenerative braking does wonders for the brakes.

          1. I just replaced the factory brakes at 173k miles on my dad’s Ford Fusion Hybrid. Only one slide pin was stuck amazingly enough. Unstuck it, cleaned it up good, fresh lube and it’s been fine.

        1. Exhaust isn’t the only emission and thats why cities that already have ice ban dates are starting to think about the tire and brake dust issue. Nothing like giving people false comfort that their air is clean when its not. When Elon makes his tunnels for electric cars if there isn’t something in place to catch or remove the dusts it will just be accumulated in the tunnels. Not every electric car has the filtering capabilities of a Tesla.
          2 min of googling would have found results for doing brake jobs wet. You know how many cans of brake cleaner it would take to remove all the brake dust from say a semi…A LOT! If you just spray brake cleaner it evaporates and leaves the brake dust where you’re working to be stirred up. Spraying a water mist every now and then keeps it where its at.

    2. My coworker has a BMW I3. The regenerative braking is so aggressive, as in the car starts regeneratively braking as soon as he takes his foot off the accelerator pedal, that he’s gone weeks without ever using the brake pedal. I think electric cars are likely to adopt a single-pedal driving strategy at some point.

      1. The new Nissan Leaf uses a single “e-pedal” in its marketing, working exactly as you described for day to day driving. Still has a separate brake pedal for aggressive braking though

      2. The Porsche Taycan has regenerative braking but it only engages when you put your foot on the brake pedal. I think you can determine how hard you have to press before the brake pads take over.

      3. Interesting… I’d think there can be a neutral position like the range of transmissions that adopted using when release the gas pedal for better efficiency and control of the regenerative breaking. Maybe some sort of inertia or accelerometer switch for automation to determine neutral or regen.

  3. After the 1970’s oil crisis, Brazil started a program to develop ethanol based vehicles, and the first car that uses 100% ethanol debuted in 1976, mainly produced from sugarcane.
    In the early 1990’s the price of sugar raised and the sugarcane processing facilities went full power on sugar production and the hortage in alcohol production was so severe that alcohol powered vehicles production fell to the verge of extinction.
    Years later the dual fuel engines (named “flex”) started to be produced and so far are the market standard for cars and light utility vehicles.

  4. TEL poisoning was a real problem. DuPont eventually implemented regular testing for lead in the employees that worked in that area. (too late for my great grandfather) MTBE (?) which was one of the replacements turned out to be quite bad as well.

    1. MTBE is methyl tert-butyl ether. It has its own problems, but it it nowhere nearly as bad as regards spewing bioactive crap into the environment that lingers for years, as TEL is.

      1. About 17 people involved in the manufacturing of TEL died of lead poisoning in 1924, spread between GM, DuPont, and a couple other smaller companies. Thomas Midgley, one of the two people who founded the Ethyl company, kept having to take vacations to recover from lead poisoning, as much as it’s possible to do so.

      2. It’s true. The workers who manufactured TEL were poisoned. However, they were exposed directly to TEL which is an organic and fat soluble lead compound, and they were exposed to very high levels of it. Leaded gasoline only contained a small amount of TEL and when it burns in the engine, it’s converted to inorganic lead salts like lead chloride and lead bromide. Those are many times less toxic and are no different than natural occurring lead salts in the soil. It was NOT the toxicity of lead that got it removed from gasoline. Unleaded gasoline has chemicals in it that are worse than TEL. It was the fact it was incompatible with the catalytic convert and all modern cars have them.

        Also Alcohol in gasoline is not without it’s adverse health effects either. It produces Aldehydes when it burns in an ICE and those are known carcinogens. Google “Aldehyde emissions from alcohol in gasoline”.

    2. The EPA mandated the use of MTBE, then a few years later sued the oil companies over MTBE contamination of groundwater from spills at gas stations. Can’t stop average driver from once in a while slopping a bit of fuel on the ground.

  5. I believe that lead also protected the valve seats in a process separate from the anti-knock properties. So leaded fuel allowed manufacturers to simply cut the valve seats in to cast-iron heads. Much cheaper than inserting hardened seats.

      1. An old friend of my father’s used to work on aircraft engines that used lead and he would sometimes talk about how part of the repairs involved scrapping the lead buildup off valves and seats. I don’t know if it was a regular thing to worry about or if was mainly some of the engines he had come in had gone too long between maintenance cycles. Nasty stuff all around though.

    1. I came here to mention the valve cushioning effect of lead.
      You got here first.
      A lot of owners of classic vehicles were adding aftermarket lead to their fuel (I think it is banned now) to protect their engines. Then a Zinc based additive was developed (which also may have been banned).
      One of the items mentioned online about Ford Flathead engines is whether a particular block has the hardened valve seats.

  6. Not sure about the “ethanol as fuel being more expensive than gasoline”. In Brazil, most cars runs completely on ethanol – made from sugar cane – and it’s price tag stays at about 65~70% the price of gasoline (while the mileage is about 20~25% lower than the dinosaur juice). Sure enough, maybe one could take into account that Brazil have large areas dedicated to sugar cane growing, and a huge refinery structure to process it. The government made a “Pro-Alchool” campaingn in the 80’s, cutting taxes for vehicles that ran exclusively on ethanol. Nowadays, the standard for Brazilian cars is to use so-called “flex” engines, which runs on any mixture of ethanol and gasoline.

    Also worth to mention: BR laws allows up to 27.5% ethanol mixed into gasoline, still being sold under the name “gasoline” – which surely made some damage on my old Yamaha CVS-650’s carburetor/cylinders due to the corrosive nature of ethanol.

    Bonus on knocking: recently, GM started selling a new model called Onix Plus (a small sendan). It was later discovered that the newer versions contained an error in the ECU, leading to excessive knocking under certain circumstances – which often caused the connecting rods to break; in some cases, the broken rods would tore a hole in the lower block, causing hot oil leakage over the exaust pipes resulting in a lot of molten plastic and scorched steel.

    1. Ethanol is more expensive if made from corn, like we do in the US. Making it from sugar is a simpler process. We make it from corn because we grow a lot of it and the corn farmers have a lot of influence on congress.

          1. I think a huge problem is there hasn’t been an advance in farming using high rises, to take advantage of less planet surface area and more volume to create more surface area, that are designed to last for thousands of years. Seems wrapping with a layer of longer lasting polymer can aid in the lifecycle of the structure… even if is planned to wrap at a later time to assure proper cure of the ferrocement or steel structure.

            That is one of the most advanced domesticated complex (and simple) technological advances in a growing society that manages large populations… gap I observe.

            Why hasn’t farming went more than simple vertical gardens for hops and maybe a few other products?

            Seems other than a few urban farms (correct me if I’m wrong, maybe there are more than I am aware of)… there isn’t much for a large scale advance in farming from a matrix and volume perspective. Seems so simple and I guess is an indicator of the Pan Troglodyte and/or ill mental traits present in the latest generation of the wealthiest and/or leadership.

          2. @jafinch78 We currently waste a lot of food, and on top of that most Americans eat more than they would like to “I can’t stop eating!” being a common expression.

            Since we already make enough to feed everyone in the world, especially if we replace the resource intensive stuff, we might not need vertical farms, although it might help.

            Biofuel in general just needs to go away as far as I’m concerned though. Any “green” tech that still involves an engine makes me think we can seriously do better.

            Engines will probably always be around for enthusiasts and specialist uses, but electric tech is usually just fantastic wherever it’s properly applied.

            All we need are better batteries!

          3. @eternityforest “We currently waste a lot of food, and on top of that most Americans eat more than they would like to “I can’t stop eating!” being a common expression.

            Since we already make enough to feed everyone in the world, especially if we replace the resource intensive stuff, we might not need vertical farms, although it might help.”

            Right… recycling in general can be improved upon (biogas generation for animal feed, fuel and fertilizer) and of course starting earlier in the process either reducing consumption and demand or improving fresher higher quality storage methods to aid in preserving like maybe CO cold storage.

            “Biofuel in general just needs to go away as far as I’m concerned though. Any “green” tech that still involves an engine makes me think we can seriously do better.

            Engines will probably always be around for enthusiasts and specialist uses, but electric tech is usually just fantastic wherever it’s properly applied.”

            Thinking to counter desertification and dust bowels along with the internal and even external combustion engines and other energy sources using solid/liquid/gas fuel(s) derived from minerals… agricultural sources are going to exist. Thinking back to my years at Michigan Tech and more than one engineer noting that you’re not going to stop the drilling of oil until it runs out since it’s so much more profitable. Amazing to see the lithium battery tech come out and finally the super and/or ultra capacitor tech come out main stream. I actually assumed that tech might be out sooner in hybrids… though doesn’t seem to have been adopted that I’m aware of main stream level yet. Barium Titanate and of course the Lithium Titanate seemed feasbile 15-20yrs ago in performance applications with batteries.

            “All we need are better batteries!”

            For sure and like I noted above (super/ultra capacitors)… surprised me with all the sodium… why sodium batteries didn’t advance and lithium was used instead. My guess was the illicit meth labs and getting rid of the Nazi method used by em to slow down the stimulated degeneration operations.

          4. @Andy Pugh “I can see an argument for switching aviation to biofuel. Given that we don’t have enough Helium to replace everything with dirigibles.”

            Using the safer hydrogen gas mix with helium might help. Same goes for external combustion engines utility. Plus the external combustion engines can be improved upon for mass production in higher pressure designs too maybe. Seems the increase in accuracy of parts or at least precision is still going on in some industries, albeit slower in others.

          5. @jafinch78: “Vertical farming” is enormously inefficient for anything needed on a large scale, which describes most farming. Want to grow tomatoes in your apartment? Fine, that can work. Wheat or corn? Try to get a tractor on the high-rise roof. Sheep or cattle would be very entertaining.

    2. Brazil is the enviable position of having various grasses and canes that, in that environment, grow like weeds and have a high sugar content. This allows the Brazilians to get a lot of good feedstock from a reasonable amount of land with little labor.

      But you cant grow sugar cane in Iowa. In the US there are varieties of corn grown just for ethanol production, but corn is a relatively resource and energy intensive plant, and, unlike cane where you use the whole plant, with corn you end up using only a small part of the plant and tossing the rest of it – and all the costs encapsulated therein.

      Until someone cracks the nut on cellulostic ethanol and allows us to use up the whole plant, corn ethanol is always going to be at a distinct disadvantage.

      At the moment, cost to produce a gallon of corn ethanol is probably comparable to, if not more, to the gasoline it replaces, and yes, Bill is right, if it weren’t for federal mandates motivated by the immense political clout of corn farmers (see: Iowa caucuses) the US ethanol market would probably be a tiny part of its present size.

      1. Ethanol from cellulose has/will have the same problem as the potential copious abundance of bio-methane and bio-methanol… the feedstock is so dirt cheap and/or free and abundant that nobody will lobby for it. Although it does have a slight advantage that oil companies can’t so cheaply make it from fossil sources and dump it on the market cheap to kill innovation in renewable supplies and protect their energy monopoly. IMO the world will run on methane and methanol when every oil and natural gas well is dry.

        If you wanna mess with it yourself, mildew and black mold breaks down cellulose, current problems are with scaling it, productionising it I think.

    3. One of the downsides of ethanol or methanol fuel and fuel additives is that a cold or improperly adjusted engine will produce acetaldehyde and formaldehyde. The former is a major contributor to lung cancer, and the latter contributes to smog (and is also carcinogenic).

      China’s having real troubles since they started producing methanol from coal to extend their fuel supply and reduce imports. Now the formaldehyde is contributing to the deadly smog in the cities.

      1. Yes, there’s some good info about this on the net. For anyone willing to read google “aldehyde emissions from alcohol in gasoline”. It’s said that 10% ethanol added to gasoline increases aldehyde emissions by 40%. In racecars that burn pure methanol or ethanol, you can actually smell it slightly. If you stand close to the exhaust it will make your eyes burn and water. Though oxides of nitrogen cause some of that as well.

  7. A combustion engine does not detonate the fuel. The fuel is combusted or burned.
    A detonation is not a controlled process. Sorry for
    being so petty but in this case it’s simply not correct.

    1. That’s why you need a high enough octane rating of the fuel. If you don’t use a high enough octane rating in an engine with lots of boost and/or compression, you can most definitely get detonation and as you point out, it’s not at all good. Anyway, the article is NOT wrong about that! The metallic pinging sound you hear is detonation. Now, you can also get pre-ignition and the 2 can go hand in hand as pre-ignition can lead to detonation because it will cause the mixture to ignite while the piston is still moving upward on the compression cycle. When that happens it leads to extreme pressures which then trigger detonation.

  8. Just a small thing: the word “detonate” should be replaced with “ignite” in almost every case in the article above.

    Detonation is a process of combustion that exceeds the speed of sound and is never-ever wanted in a spark ignition engine as it causes damage to the engine components. Diesel engines are built much tougher and can absorb the additional forces although they are heavier and slower as a result.

    In a gasoline engine you want a smooth ignition-combustion process, never a detonation.

    As an example, gunpowder ignites, combusts and pushes a bullet out of a gun. TNT detonates and would simply split a gun barrel if used that way.

    1. Diesel engines do not operate under detonation either. The diesel is sprayed in droplets that burn from the outside in. The engines are built tougher to handle the higher compression ratio, not to handle detonation.

      Detonation happens when the fuel ignites at multiple points due to compression heating and burns all at once. This doesn’t happen in a diesel engine because the fuel is not pre-mixed with the air. That’s not to say diesel engines can’t knock or ping – it’s just takes special conditions to happen.

      1. The main reason for diesel engine knocking appears to be when the engine is cold, or the fuel is improperly atomized and mixed, or when the fuel cetane number is too low (doesn’t ignite easily enough). All these cause the fuel to accumulate in the cylinder and ignite with a delay over the next compression cycle.

  9. I think that you should be more careful about your use of the word ‘detonation’.

    In an internal combustion engine, the air-gas mixture is supposed to burn with a deflagration / to combust. That is to say, the flame propagates at subsonic speeds
    On the contrary, with a detonation, the flame front moves at supersonic speeds. A detonation (for example due to auto-ignition) is undesirable as it produces a shock-wave. The shock-wave is the one causing the damages.

    The article should read: “ideally the air-fuel mixture that gets injected into a cylinder will detonate at the perfect moment” -> “deflagrate”/”burn”/”combust”. I don’t think that detonations occur in a Diesel engine either (I might be mistaken here).

    If you want some more information on the difference between deflagrations and detonations:

    I also might be missing something here and the word “detonation” has a different meaning in the automotive industry …

    1. I think that “detonation” _does_ have a different meaning in the context of automotive engines.
      It is certainly a word I have heard many times used to refer to unwanted compression-igntion in petrol engines.

  10. Quite like Ferrocene. Used it for years to keep an old MG trundling about. Would have preferred MMT, but it was more expensive from Sigma.

    Car was set up to run well in winter, then in summer, with the hotter weather, a wee octane boost discouraged it from knocking.

    To jump on the detonation vs deflagration bandwagon. When studying the transition from one to the other in aircraft fuel systems, spent weeks not knowing whether an experiment would burst into pretty flames or make a very loud bang. Amusing but tense!

  11. 1975 was the year most US vehicles had to run on unleaded gasoline. That was the first year for catalytic converters. An exception was made for “one ton” trucks because those were often sold as cab and chassis, for another company to install a flatbed, van box, wrecker crane etc onto.

    It wasn’t possible to test every combination so the EPA decided to test none, and require no emissions controls on one ton (or heavier) trucks until sometime in the 1990’s. That loophole is how Dodge made the Warlock and Lil’ Red Express pickup trucks with powerful engines, no AIR pumps, catalytic converters, exhaust gas recirculation etc.

    Since California’s laws require all 1975 and newer vehicles to retain their factory original emissions control configuration, despite the federal 25 years and older exemption, CA can’t require emissions controls to be installed on the unregulated one ton trucks that never had them. If you want to build a do whatever you want hot vehicle in California but also want something newer than 1974, start with a 2 wheel drive one ton truck that never had emissions controls.

    I remember in the late 70’s and early 80’s it was still possible to find gas stations that didn’t have any unleaded fuel, almost up until leaded fuel was banned completely for on road use.

  12. “diesel engines require lower octane fuels, as they only compress air, with the fuel being injected at the end of the compression cycle, with the heat from the compressed air igniting the fuel”
    This puzzles me ! (and disappoints me quite a lot as it is far from the usual accuracy out there, this could deserve publication in The Sun, excluding page 3 :P))
    – Diesel fuel has NO octane (diesel fuel is a mix, whose average composition is C12H24, far from C8H18 aka octane).
    – Diesel engines are a type of self-ignition engine, that’s why they don’t need a spark plug to run (only pre-heating to start). 2-strokes model engines use a mix of oil (2-strokes demands), ethanol and ether)
    – Injecting fuel at the end of the compression cycle is afaik called direct injection, nothing to do with diesel/gazoline/ethanol being used, even-though it was first introduced on diesel engines before been more widely used. on ICEs.
    My 5 cents ;)

    1. Diesel might not contain much or any octane, but it can still be tested to determine the “Octane Number”
      Puts the RON of diesel fuel at 25, so that’s definitely low.
      Which seems counter-intuitive. It suggests that diesel in a petrol / gasoline engine would pre-ignite horribly. A surprise given their relative volatility and flammability.
      I wonder if petrol in a diesel engine burns? (I know that it damages the pump due to lower lubricity, but does it even run? It’s not an experiment I have ever done, though I did once do the reverse)

      1. Pre-ignition in a petrol engine is the fuel igniting from the heat of compression, without needing a spark, right? Which is basically the design principle of the diesel engine. So it’s not surprising really. Though yes given diesel’s lower volatility you might expect it to be less “keen” to ignite, you can throw a match into a puddle of diesel and it just goes out.

        But that’s all at STP. The pressure and temperatures in a combustion cylinder are a different sort of environment altogether (“a different sort of…”). So that makes sense too.

      2. Sometimes Wikipedia is great, sometimes not so much… This time, the intro is mostly wrong setting the problem a biased way. nonetheless, you’re free to believe it.
        And BTW, this not ethanol but kerosene/lamp oil for diesel two-stokes model mix. My bad…

      3. Diesel is rated by the cetane number, which is the rate of combustion speed. It basically measures the ignition delay of the fuel under compression. The higher the number, the lighter the oil and the easier it is to ignite.


        This works a little different from gasoline, because diesel oil isn’t so volatile – it doesn’t evaporate much, so it doesn’t flash over like gasoline. The flash point temperature is higher, so it can be both less volatile and still easier to ignite – once it evaporates.

        1. Point being that while a fuel might readily take off into vapors, there might still be a high threshold energy to break the bonds before it starts to combust. That’s the point behind high-octane fuels like Toluene – the molecule is relatively light, but there’s a closed cyclic bond that you need to break first before it ignites.

          Cetane works the opposite way – you may have a heavy long chain molecule that’s basically like cooking oil, but because it’s highly branched and ready to join with oxygen molecules, it has a low threshold energy and it ignites readily under compression.

          There’s an almost inverse relationship between the cetane and octane numbers – if you mix enough gasoline in with diesel, even assuming it won’t harm the distribution pump, it will destroy the engine because the gasoline will ignite with a long delay and cause detonation.

          1. There’s an old truckers trick to mix gasoline with diesel for cold weather, but this doesn’t help the engine run any better – its main effect is to dissolve the waxes when the temperature goes below the cloud point of the fuel, so the fuel filter won’t clog up.

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