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Why is 100LL so much more expensive than gasoline for cars?

I get the fact that it's 100LL, instead of 87, 91, etc.

For example (as of now, 13 Oct 14), the 91 unleaded gas at my local gas station is 3.41USD, and the 100LL at my local airport is 5.49USD (for the self serve).

What's the reason for the huge increase in price between car and aviation gas?

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    $\begingroup$ tighter standards, and the tax on leaded gasoline $\endgroup$ – ratchet freak Oct 13 '14 at 21:23
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    $\begingroup$ Is that in USD per gallon? $\endgroup$ – DeltaLima Oct 13 '14 at 22:00
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    $\begingroup$ I'm not trying to be sassy, as I'm sure also weren't, but I think it's fairly obviously I meant usd/gal. $\endgroup$ – Keegan Oct 13 '14 at 22:15
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    $\begingroup$ @KeeganMcCarthy For people outside the USA it may not be obvious what units you fuel your aircraft in. For making a comparison it helps to have the units right. So here we go: 2.74 EUR per litre including taxes at the local airport. That is 13.17 USD/gal. You said expensive? :-) $\endgroup$ – DeltaLima Oct 14 '14 at 8:17
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    $\begingroup$ Though it's an old question, let me add prices for car gas. Here, we currently have 1.58€/l = 6.59USD/gal. $\endgroup$ – sweber May 22 '15 at 23:09
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The LL of 100LL stands for Low Lead as it has tetra-ethyl lead added as a detonation inhibitor for high-performance engines. Despite the "low" moniker there actually is a lot of it in there, and it's toxic. This fuel is expensive for a number of reasons:

  • The lead itself is expensive
  • The lead additive means that a refinery must shut down and clean the lead before producing other fuels, this means more refinery time and therefore more costs
  • Lead in fuel cannot be allowed to contaminate other fuels so you cannot pipeline leaded fuel. It has to be transported in containers, adding to shipping costs
  • There are extra controls around the lead in many parts of the world, namely storage requirements and paperwork, all which costs
  • 100LL fuel has many more "aromatic" hydrocarbons than mogas (auto fuel) in order to increase the octane levels and prevent fuel from vaporizing in your lines at high altitude. It's much higher grade, so it costs more
  • It's a specialist fuel made in much less quantities than other fuels, so a premium is added to ensure a profit

Keep in mind that the Avgas is taxed less than Mogas in most places. It would cost even more if it were taxed the same!

Efforts are underway to come up with a 100LL replacement that will work the same in all engines and situations, which is a hard problem to solve. Whatever fuel they come up with, while having no lead, will still likely be more expensive than mogas just because of the more expensive hydrocarbon mix and the specialist nature of the fuel.

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    $\begingroup$ Not at all! The lead prevents high performance engines from tearing themselves apart because of detonation, when fuel explodes in the cylinder prematurely. It's still there because nobody has found a substitute which will work the same that isn't as toxic and expensive. $\endgroup$ – GdD Oct 14 '14 at 12:47
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    $\begingroup$ Yes, it was added as an anti-knock agent. Modern auto engines are much more sophisticated than most aircraft engines, with automatic mixture control, fuel sensors, etc. Better technology means better detonation control. Aircraft engines are not only less sophisticated but some also operate at more extreme conditions than cars, like 15,000 feet. $\endgroup$ – GdD Oct 14 '14 at 15:39
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    $\begingroup$ Not all countries have the same pollution-control standards as the U.S., and TEL is a fairly inexpensive antiknock compound which is attractive to poorer countries. The Chinese are reportedly still making some leaded grades, and it's still used in some other developing countries, mainly Africa. $\endgroup$ – KeithS May 22 '15 at 22:27
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    $\begingroup$ @SpongeBob: In part yes. The anti-knock compounds used in unleaded fuel also produce pollution that is reduced by the catalyst. Cars were generally upgraded to have catalyst and burn unleaded fuel. Aircraft don't have catalysts, so they still burn leaded fuel (plus there are other slight differences in properties that don't allow using one type of fuel in engine designed for the other). $\endgroup$ – Jan Hudec May 24 '15 at 9:50
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    $\begingroup$ I didn't say VOCs @zymhan, I said aromatic hydrocarbons. They are called aromatic because many have a sweet smell, not because of volatility. Some aromatics are more volatile than others. $\endgroup$ – GdD Apr 4 at 17:38
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The distillation and refining process for 100LL is more expensive than the process for 91 unleaded.

100LL has a high octane index, and is treated to be less volatile (in particular at high altitudes). 100LL is also perfectly dry in order to prevent icing.

Also, 100LL is produced in smaller quantities than car fuel, so economies of scale are also a factor.

In fact, due to the high price of aviation fuel, certain low-powered engines can be certified to fly with the same gas you put in your car.

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  • $\begingroup$ there's also far less avgas refined, because there is far less demand than for mogas, and that raises the cost to produce a given quantity (say, a gallon). $\endgroup$ – egid Oct 13 '14 at 21:54
  • $\begingroup$ Thanks! The lower demand is something that I didn't think of. And it's probably the largest reason. $\endgroup$ – Keegan Oct 13 '14 at 22:17
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    $\begingroup$ Another factor is you cannot transport leaded gas in the same container trucks as unleaded gas because of contamination (i.e. lead getting into unleaded fuel) issues. $\endgroup$ – JerryKur Oct 13 '14 at 22:23
  • $\begingroup$ Due to high price of avgas (JetA1 is not expensive) new designs are coming with compression-ignition engines that burn either automobile diesel, JetA/JetA1 or either. $\endgroup$ – Jan Hudec Oct 14 '14 at 7:02
  • $\begingroup$ There are non-leaded Avgas variations available. One example is 91/96 UL. STC-s are available for most or all normally aspirated engines from Lycoming and Continental. But as the high performance engines on larger machines having turbos needs 100LL it is generally not available. $\endgroup$ – ghellquist Jan 16 '18 at 6:39
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What's the reason for the huge increase in price between car and aviation gas?

There are many differences, as other answers mentioned, but not as big as the experienced prices show. But by only focusing on the product it's easy to miss cost involved in distribution and sales.

An FBO has at least the same, usually much higher, fixed cost than an average gas station which need to be spread over a much lower number of customers. The fact that a C172 needs more gas (like 50 vs. 15 gallons) isn't much of a relief either.

In addition I don't know of many gas stations providing a lounge, free coffee (and sometimes sandwiches), internet access, flight planing tools and so on, all the way to courtesy cars.

All of this leads to a higher price per gallon than what's caused by the raw gas alone. The effect can be easily seen where auto gas is offered for ultralights, or diesel for capable engines. They carry a visible mark up compared to the gas station next door.

Then of course there's the same effect that lack of competition has on auto gas. Fields with a single FBO are often priced much like the sole gas station on a lengthy stretch of highway ... slightly above average.

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protected by Federico Nov 28 '17 at 20:58

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