GA’s Catch 22

Why don’t FBOs sell auto fuel? When will unleaded avgas be available — and who will sell it? These questions, and more, abound about aviation’s Catch 22: FBOs will not stock unleaded fuels until the market supports it — and the market will not develop until the fuels are readily available.

A fuel system at an FBO is an expensive thing to install and maintain. Today, it is necessary for FBOs to offer 100LL, as that is the major demand. If an FBO decides to sell a second grade of avgas, then it would need to install a second (or third, if it handles Jet A) fuel tank, filter, pump and related equipment. With all of the requirements for containment, etc., this is a very costly option — and an option that probably will not pay for itself at this time.

If 100LL goes away, leaving only one grade of unleaded avgas, the FBOs will have no use for a second system. There also is the problem of having multiple systems, which increases the chances of misfueling.

As we look into the future, my best guess is that, if we go unleaded, there will only be one grade of unleaded fuel. It would be nice to have multiple grades, but the general aviation market is just too small to economically support more than one grade of avgas.

So what will happen with the new fuels? Basically nothing.  I do not see a significant shift away from 100LL until the government finally says “no more” — and there is logic for this. As long as 100LL is available, very few people will be willing to pay more (or the same) for an unleaded product that may or may not work as well, will have lower octane than 100LL, and may require significant modifications to their engines.

So what is being done? ASTM International is working on several new specifications. This is necessary so that companies that are developing new engines and/or modifications to existing engines will have a firm target on which they can design new products. These systems will be tested and finally offered to the flying public.

There will be a time that these modified aircraft will need to use 100LL as that will be the only product available. Then when — or if — 100LL goes away, they can be switched over to the new unleaded fuel. These modified engines, along with all of the lower compression ratio engines in the fleet, will be able to switch over to the new unleaded fuel as it becomes available.

The big problem is who will be responsible for all of the older — especially the rarer — engines where the manufacturer is no longer in business and there are not enough of them for an engine modifications company to work on? Also, who is going to check every aircraft to ensure that it is OK to fly on the new fuel? And, more important, who will be sued when there are problems with the new fuel?

To make matters worse, most experts, including myself, thought that the biggest problem with low octane fuels would be in turbo-charged engines. It seems that high compression ratio non-turbo engines may also be a problem and may be more difficult to modify than some of the turbo engines.

Much of the problems with modifications to any engine is that you can reduce the octane requirement of any engine by de-rating it, but this can be a real safety issue. That’s why most companies are trying to modify engines in such a way as to reduce the octane requirement and still make the same power. This is a more difficult and probably more expensive problem.

On the positive side, the engine companies are working on the problem, and a solution should be available for most, but not all, engine models. And notice, I said available, not necessarily inexpensive.

Ben Visser is an aviation fuels and lubricants expert who spent 33 years with Shell Oil. He has been a private pilot since 1985. You can contact him at


  1. Karl D says

    Just to add to that though, Instead of building large tanks on the airport, stratigically place it at another loction to store lots of Mogas to service many airports. Use the smaller gas trucks to service the airport region.


  2. Karl D says

    If a CO-OP had a fuel truck and picked up Mogas from the refinery. They could service an area of airport. The owners (or through cooperation with the FBO tie down company) could arrange to fill up a customer’s fuel tanks. That way, we would not have to have extra ground tanks at the airport. Demand might not be great at first, but if it is possible and cheaper than 100LL, it might catch on. Once airports see that people are starting to use it, they might consider the feasibility of Mogas. Just a thought.


  3. says

    Visser’s comments are always refreshingly honest and we, the authors of the GAFUELS blog on this site, appreciate this greatly. As much as we’d like t believe that 100LL will be with us for a long time, this administration has a track record for being “unconventional” – all bets are off. On Visser’s other comments – we have spoken with many FBOs and interest in a 2nd fuel system does exist. Some are eager to have one for ethanol-free Mogas, but their airport authorities are not. Most report zero interest from their current suppliers of 100LL and Jet-A. There are today however turnkey self-serve fuel systems available at a significantly less cost than the large tanks one normally finds. Why wait though for the FBO? Perhaps groups of pilots could form CO-OPs to supply themselves. The real impediment, we believe, is to find a reliable supplier of premium ethanol-free mogas. This fuel could be used by 70%-80% of the entire piston-engine fleet including most old radial engines and virtually all new LSAs, the future of sport aviation and flight schools. Watch our blog GAFUELS for information as we try to find real solutions ASAP.

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