In my last column, “Birds of a feather,” I wrote about the need for an ASTM standard for any new unleaded replacement for 100LL.
I also noted that a committee has been working on a new specification for about 25 years and ASTM is now looking at issuing a separate spec for each individual fuel manufacturer.
I have received several questions from readers asking what the difference is between an ASTM spec and qualifying a new fuel using an STC.
The problem with using an STC is that after 100LL is gone, pilots who are flying cross-country and land at an airport that is supplied by only an STC qualified fuel will not be able to purchase that fuel if he or she does not have the necessary STC.
I feel that it is important that all new unleaded replacements for 100LL be ultimately approved for all applications by all active manufacturers.
An STC approval may work for a start-up, but by the time 100LL is fully eliminated, the replacement products need to be qualified against an approved standard. This standard (or standards) need to be acceptable and agreed upon by all parties, including the FAA, the engine manufacturers, and the airframe manufacturers.
The most common suggestion I have received concerning the future of unleaded avgas is that there is a need for two grades of fuels, not just one.
Most pilots feel that there should be a new 100 octane unleaded fuel to replace 100LL and a second grade for either an auto fuel-based product or a 94-octane fuel based on just removing the lead from the current 100LL. (Swift Fuels already has a fuel, UL94, that meets ASTM D7457.)
In the 1990s, the man in charge of fuel requirements at Cessna, Cesar Gonzalez, felt that the future of general aviation — and especially sport aviation — rested on the availability of a non-boutique fuel derived from the readily available pool of automotive gasoline.
That led to the development of ASTM D6227, “Standard Specification for Grade 82 Unleaded Aviation Gasoline.”
While the spec had limits on ethanol and other oxygenates, it was basically just regular unleaded auto gas.
The spec was approved by ASTM, but I believe is not being used at this time.
I suggest the industry and regulators, including those involved in the Eliminate Aviation Gasoline Lead Emissions (EAGLE) initiative, work to get the 82UL spec active again.
Then the members of the General Aviation Manufacturers Association (GAMA) could approve the fuel for all 80/87 engines in the fleet, plus all of the sport aviation aircraft.
Next, the National Air Transportation Association (NATA) could encourage all FBOs and fuel distributors to make the fuel widely available.
Many FBOs already have the facilities to handle two grades of avgas, but others may need to add some equipment.
The big problem here is sourcing non-ethanol auto fuel. However, auto fuel containing ethanol cannot be shipped in pipelines. This means that non-ethanol fuels are available at all distribution facilities even if a state requires that all auto fuel contain ethanol.
Once 82UL becomes available and pilots become aware of it and know that it is approved for their aircraft without an STC, I believe that the sales and benefits will become very significant.
For example, the economic benefits for pilots will be very real. According to a recent Google search, the average price for 100LL in the US in early October 2023 was $6.93 per gallon. The estimates for one of the 100 octane unleaded fuels say it will cost between 50 cents and $1 more a gallon than 100LL.
However, the present price for regular unleaded auto fuel is about $4 a gallon vs $7.50 for an unleaded 100 fuel, saving pilots about $3.50 a gallon.
If a pilot flies 100 hours a year at 8 gallons an hour, that is a significant difference, especially for working class pilots who just want to go for a $100 hamburger and not a $200 hamburger.
There will be some additional costs with 82 UL fuel, such as handling and shipping, plus storage at dedicated facilities.
However, these can be offset by refunds of road taxes. If an auto fuel is sold for a non-road use, such as in aircraft, the state and federal road taxes can be refunded.
The bottom line
Approving 82UL is not the total answer and it is not the grandiose solution for all of GA’s unleaded fuel problems. But it will help ensure a continued supply of an approved, reasonably priced fuel for part of the GA fleet.
And it will significantly reduce the amount of lead being emitted into the atmosphere, which is one of the goals of the EAGLE program.
The other option is to do nothing and wait for a fully approved unleaded replacement for 100LL.
But based on past performance, how long will that take? And how will that affect the costs associated with flying a GA aircraft?
Take that one step further: How will that wait and uncertainty affect the number of people going into or even staying in flying?