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83 votes
Accepted

Why is jet fuel cheaper than piston fuel?

Jet-A (and all turbine fuels) are far cheaper than 100LL (at least in bulk; retail prices vary due to local supply and demand as well as different regional tax regimes on aviation fuel) for several ...
UnrecognizedFallingObject's user avatar
31 votes

Why is jet fuel cheaper than piston fuel?

There are a number of factors that go into it: Economies of Scale Jet-A is used in a much higher volume than 100LL. All the jet engine commercial aircraft each day burn through orders of magnitude ...
Ron Beyer's user avatar
  • 36.2k
25 votes
Accepted

How to safely handle AVGAS (100LL)?

If you don't crawl underneath and breathe in the exhaust fumes from the engine, you'll be fine. If you do crawl underneath and breathe in the exhaust fumes, you'll be dead from carbon monoxide ...
John K's user avatar
  • 132k
20 votes

Can I assume that AVGAS can be used without any problem when the engine manual suggests RON 95 or higher?

Yes it will run fine, but... Lots of drag racers use Avgas in their cars to get the octane rating to run 12 - 14:1 compression ratios in high performance engines (At the airport I used to hang out at ...
John K's user avatar
  • 132k
16 votes

Avoiding leaded gasoline in aviation

You could fly gliders. They don't use leaded fuel. In fact, they don't use fuel at all.
60levelchange's user avatar
13 votes
Accepted

Can I assume that AVGAS can be used without any problem when the engine manual suggests RON 95 or higher?

This question comes up regularly in automotive circles. There is no advantage to using fuel with higher octane number than your engine requires, though in automobile engines there may be a minimum and ...
Zeiss Ikon's user avatar
  • 17.1k
10 votes

Why is alcoholic gasoline such a showstopper for aviation?

The modifications required are just not economically viable. The main issue is vapor lock, because ethanol has a lower vapor pressure (i.e. more likely to vaporize) than gasoline. Worse, mogas ...
StephenS's user avatar
  • 27.7k
9 votes
Accepted

What is the freezing point of 100LL Avgas?

ExxonMobil China says their Avgas 100LL will not freeze above -58°C. The 'typical' freezing temperature is not given, but I would expect we'd be more interested in the maximum freezing temperature.
Spehro Pefhany's user avatar
8 votes
Accepted

Avoiding leaded gasoline in aviation

J. Hougaard's answer is a bit of a smart @ss but it is one way to fly without using leaded fuel minus whatever is burned in the engine of the tow plane. But there a few more alternatives as well. Do ...
Romeo_4808N's user avatar
  • 74.1k
8 votes

Avoiding leaded gasoline in aviation

This is a long answer but I think it explains a viable, realistic alternative to 100LL and Jet-A. There is a common alternative to 100LL: regular gasoline! Many airplanes, particularly trainers, can ...
acpilot's user avatar
  • 6,016
7 votes
Accepted

Do different grades of leaded avgas differ in ways other than their lead content?

Gasoline (both avgas and mogas) grades are distinguished solely by octane rating and lead content. In theory, the octane rating is the amount of actual octane (C8H18) it contains, with the remainder ...
StephenS's user avatar
  • 27.7k
6 votes
Accepted

What implications does automobile electrification have for the supply and cost of Avgas?

I have not seen any studies on this, nor would I expect to as Avgas is such a niche product and the price of it is not heavily dependent on the price of the underlying fuel itself. If you look at this ...
GdD's user avatar
  • 54k
5 votes
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Effects of lead on engines and engine oil

Yes theoretically you could put catalytic converters on airplanes running unleaded avgas and reduce those compounds. It isn't going to happen because the overall impact is too small to make up for ...
John K's user avatar
  • 132k
5 votes

What happens if you put car gas in an airplane?

First, it's important to note that the octane rating for aviation gas has nothing to do with the octane rating for car gas. This is because octane isn't calculated, it's measured. A specialized piston ...
HiddenWindshield's user avatar
5 votes
Accepted

Does a diesel piston engine's power decrease more slowly with altitude than with an AVGAS engine?

Welcome to the community! Because the Austro Engine AE-300 is a diesel engine,(JetA/Kerosene and Diesel are very similar) it is equipped with a turbocharger. Turbochargers compress the engine's intake ...
JetCityMatt's user avatar
  • 1,125
4 votes

Why is alcoholic gasoline such a showstopper for aviation?

The main issue, the one that bans ethanol blend fuel for use under the autofuel STC, is the effects of ethanol on rubber components in the fuel system. Ethanol is also mildly corrosive to aluminum ...
John K's user avatar
  • 132k
4 votes

What is the Difference between mogas and avgas?

The main difference is avgas is based on completely different chemistry, paraffin (the flammable component of candle wax) and mogas is based on aeromatic hydrocarbons (like benzine). (Forget about ...
John K's user avatar
  • 132k
4 votes

What is the Difference between mogas and avgas?

Chemically speaking, The difference in the fuels is the inclusion of lead-based additives that increase the Octane rating of the fuel, which are otherwise banned for use in other settings due to the ...
user44968's user avatar
  • 117
2 votes

How should Isopropyl Alcohol be used as an AvGas Fuel System Icing Inhibitor?

I fly a PA-30 Twin Comanche regularly,and,since the POH does not discuss use of isopropyl alcohol or Prist,have contacted Piper repeatedly to seek approval.No response has come from Piper.AOPA and Int’...
Chaz's user avatar
  • 21
2 votes

Why is AVGAS so much more expensive than car gas?

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 ...
Raffzahn's user avatar
  • 555
2 votes
Accepted

Why does the FAA not support UL102 (formerly 100SF) unleaded av-gas as an alternative to 100LL fuel?

The problem is basically bureaucratic delays, helped along by easing of EPA timetables on the banning of leaded fuel, taking some of the pressure off, which has caused the developer of UL102, Swift ...
John K's user avatar
  • 132k
2 votes

Why is alcoholic gasoline such a showstopper for aviation?

The Rotax line of engines are engineered to use premium automotive pump gasoline with 10% ethanol. Their engines can also use AVgas, but that tends to load the oil with lead and requires more frequent ...
Steve's user avatar
  • 21
2 votes

What happens if you put car gas in an airplane?

It depends on the engine type and the fuel the engine manufacturer has designed it for. In the Cessna 172S PIM, it says: WARNING Use of unapproved fuels may result in damage to the engine and fuel ...
SMS von der Tann's user avatar
2 votes

Does a diesel piston engine's power decrease more slowly with altitude than with an AVGAS engine?

It is not because it is a diesel engine, though diesels are more likely to be designed that way. The engine is so called “flat rated”. That means its power is not limited by simply not being able to ...
Jan Hudec's user avatar
  • 56.3k
1 vote
Accepted

What happens if you put car gas in an airplane?

It depends. If the anti-knock rating is too low for the engine conditions then you will get detonation, which both limits power and causes major internal engine damage. ("octane" is a common ...
Max Power's user avatar
  • 2,604
1 vote

Does a diesel piston engine's power decrease more slowly with altitude than with an AVGAS engine?

It's all about the air compression! The graph that you mention shows two diesel/jetfuel geared piston engines, and one avgas direct drive piston engine, the Lycoming IO360. The two diesel engine ...
Koyovis's user avatar
  • 61.8k
1 vote

What is the Difference between mogas and avgas?

Mogas and avgas are very similar ; the difference is in ratio of high octane to lower octane components . The major group of high octane components are aromatics; the xlyenes with octanes well over ...
blacksmith37's user avatar
1 vote

Do different grades of leaded avgas differ in ways other than their lead content?

Octane is is used as a reference only. That is to say 100% iso-octane (branched molecule) has an octane value of 100 by definition. A mixture of 100% heptane (straight chain) has an octane value of ...
APL's user avatar
  • 11
1 vote

Why is alcoholic gasoline such a showstopper for aviation?

It's not just big twins that have "high compression" or use turbos. Many four and six seat engines have higher compression engines also without turbos. My Lycoming O-360-A1F6D has no turbo. has 8.5:1 ...
CrossRoads's user avatar
  • 8,795
1 vote

How small can turbojet engines be made whilst remaining fuel efficient, light, cheap, and producing enough thrust to carry a human, gas, and casing?

The figure of merit here is thrust to weight ratio (https://en.m.wikipedia.org/wiki/Thrust-to-weight_ratio) For a good turbojet, you get about 5:1. So a 100 lb engine could produce about 500 lbf of ...
Daniel K's user avatar
  • 5,518

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