The fuel of the future

As all pilots know, you go to Oshkosh to find out what is new in aviation. But if you want to know what’s new in aviation fuels, you go to an ASTM meeting.

ASTM is the organization that is in charge of the specifications for just about everything. If you buy a gallon of Jet A almost anywhere in the world, it will be certified to meet the ASTM D-1655 specification requirements. Likewise, if you buy a gallon of 100LL, the list of tests and the limits that the fuel must meet are defined by the ASTM D-910 specification.

The other part of this is if you have an aircraft that is certified on 100LL specification fuel, you must use only fuel that meets this specification, or use a fuel that has been STC’d for your aircraft.

This means that if a new unleaded fuel is introduced, an ASTM specification must be created to “define” what the new fuel is and what specifications it must meet.

So what is the industry working on?

No surprise, it is working on a specification for a 94 minimum lean rating fuel that looks a lot like the present 100LL fuel, only without the lead.

As I have been saying for years, this is the only logical step for an unleaded fuel that can be manufactured conventionally, and will cause a minimum of problems if 100LL is outlawed. It will not be an invisible change but, hopefully, a manageable one.

So when will the new fuel be available? That is a question that depends on the folks in Washington — and they have no idea.

The ASTM is starting to define the fuel so that a reference fuel can be blended. This will allow engine manufacturers and engine modification companies to start working on the needed technology and systems so that once a regulation against leaded avgas does arrive, engines will be available to operate on the new fuel.

This makes a lot of sense and I applaud their efforts. This is not a complete solution and it does not absolutely preclude all other fuels from being considered, but it does define a starting point on which the industry can design future systems to operate safely.

If you are a betting person, this is the odds-on-favorite to become the fuel of the future.

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. JB Wood says

    Dear Ben,

    I ran across your site and am hoping to make contact with you. Thank you and God bless you & your family,

    JB Wood

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