For years, there has been clamoring for airplanes to get rid of lead in piston engine Avgas. In the early 2000s, Thielert created a Jet A burning piston engine for Diamond Aircraft that gained some traction, but Thielert had internal issues and ended up declaring bankruptcy. Several other Jet A piston engines have come down the line since then to some success (Diamond is currently using 2 Austro manufactured Jet A piston engines on it’s DA62 and a Continental manufactured Jet piston on the new DA50).
The problem with a Jet A burning piston engine, though, is that those engines would be very expensive to put on existing airplanes, not to mention the cost of the STC alone.
Insert GAMI (General Aviation Modifications, Inc.), the famed Ada, Oklahoma company that championed turbo normalization, balanced injectors, and lean of peak operations. For those that have been to GAMI’s engine class, you know that these guys are at the very top of their game in engine knowledge.
In 2010, GAMI started the process of creating an Unleaded form of Avgas, terming it G100UL (the irony of traditional Avgas, 100LL, is the LL starts for low lead, but the lead levels in 100LL are actually quite high. UL stands for UnLeaded). Just before Osh Kosh in 2021, GAMI revealed that it’s work has come to fruition, gaining an STC for G100UL for Lycoming powered Cessna 172s.
The amazing thing about GAMI’s product is that it is able to mix with 100LL and not cause any issues. This means fuel trucks, fuel lines, fuel pumps, and aircraft fuel tanks don’t have to have any modifications to them to use G100UL. Plus, pilots will see longer engine life using G100UL because of the simple elimination of the lead. In tests, combustion chambers in cylinders burned cleaner, so theoretically, cylinders and engines will last a lot longer.
According to the company, GAMI has a few more tests to run and, assuming those go well, G100UL will be available for a whole lot more airplanes. An STC will still be required for the use of G100UL in a specific airplane, but the hope is, eventually, 100LL will be completely replaced by G100UL. The only downside is that G100UL is expected to cost about $1/gallon more than 100LL.
GAMI has partnered with Avfuel, so expect to see 100UL showing up at all Avfuel FBOs in the next year or two.
To read more, check out the press release on AOPA’s website.