G100UL: The future of fuels

For the past couple of years, George Braly and Tim Roehl, owners of General Aviation Modifications Inc. (GAMI), have been thinking about the future of avgas. Now the two are creating the future, having recently filed a patent and STC for an unleaded 100-octane avgas they call G100UL.

Unusual for the aviation industry, actual development of the fuel began just a few months ago, with the company hitting pay dirt on its first attempt.

The search for a replacement for 100LL has been going on for years, starting in the early 1990s when the EPA phased lead out of automobile gas. The aviation industry was given an exemption for 100LL while it looked for an unleaded alternative. Time passed and not much was accomplished, then in 2007 the Friends of the Earth filed a petition with the EPA, claiming avgas endangers the public health and welfare. The petition required the EPA to take action. But even then, the industry didn’t make much headway into developing a new fuel, even when EPA officials said during forums at the big shows, including Oshkosh and the AOPA Aviation Summit, that time was running out.

“It just wasn’t pressingly important,” Braly said, noting that all changed at the AOPA show in Tampa. He attended a forum where an EPA official talked about its efforts to phase out 100LL. After the forum, somebody asked the EPA official if he was getting much cooperation from the industry. “I saw the look on his face and it actually made me take a step back,” Braly recalled. “It made me realize ‘this guy is serious.'”

In fact, EPA officials are serious, now saying a notice of proposed rulemaking could be seen as early as October, with a targeted phase-out date of 2017.

After the forum, Braly tracked down Mark Rumizen, a reciprocating engines/fuels specialist with the FAA, who had also been on the panel. He asked if he tried to come up with an unleaded avgas, could it be certified by STC. “He said he preferred ASTM standards, but we could do it by STC. I said, ‘good, I’ll go home and try that.'”

Braly and Roehl returned to Oklahoma and went to work. “The first thing we tried worked,” Braly said, “We’ve tweaked it five times since and every time except once it’s gotten better and closer to where we want it to be.”

What may seem like beginner’s luck is anything but.

“We had a big head start,” said Roehl, noting the company has tested a variety of fuels developed by others in its engine test cell. It’s also participated at the ASTM level. “Over the years, we’ve watched the industry try and make a determination of what unleaded avgas might be.”

Braly and Roehl didn’t like the choices the industry was leaning towards — Swift Fuels, a biofuel that is in the beginning stages of development and “has a long way to certification and production,” Roehl said, or “94UL, which just doesn’t have the ability to operate high performance engines.

“We didn’t think the industry should suffer,” he continued, “so knowing what is in avgas and what is in the additives, we began to formulate blends to see what we could come up with.”

Happy with their first attempt, the pair filed for an STC to certify the fuel for use in a turbonormalized Cirrus SR22. While the two also filed for a patent, they aren’t waiting for that to be approved to move ahead. “The benefits of the STC are that the proprietary nature of the fuel will be maintained,” Roehl said.

The pair won’t divulge what’s in the fuel — calling it a secret formula like the formula for Coca-Cola — but Braly noted “there is nothing in it that hasn’t been running in airplanes in the past.”

In fact, G100UL will be a drop-in replacement for 100LL. It can be mixed in any percentage with 100LL, so if a pilot wants to top off a fuel tank that already has 100LL with G100UL, there will be no problem. “The fuel in the plane will still retain its spec and integrity and there will be no degradation in performance,” Roehl said.

Because it is a drop-in replacement, a separate distribution network won’t have to be created — as it would with a biofuel — and FBOs won’t need to add another fuel tank. “We know that FBOs operate on a shoestring,” he said, “so we don’t see them investing in a second tank.”

GAMI doesn’t intend the produce the fuel, but to license the formula to refineries. And Braly believes that more refineries may get into the avgas business.

“Refineries now don’t want to deal with avgas because they don’t want to deal with lead,” he said, noting only six or seven refineries still make avgas. “That may expand with this new fuel.”

But what’s the bottom line for pilots? “We won’t know until we know,” Braly admitted, but said, “we’ve found no reason why this fuel should be more expensive than existing avgas by any numbers more than 10 to 20 cents a gallon.”

For more information: GAMI.com.


  1. Nick says

    It would be great if instead of another price increase, we could see lesser costs due to more refineries producing resulting in lower transport costs, no lead resulting in easier handling and lower costs, etc. Regardless, it is great to see an alternative close at hand. Any chance the octane rating will actually be INCREASED, for use in 115/145 engines? Any downsides to this proposed fuel known at present?

  2. says

    Well this is good to hear too. I’ve seen a fair amount of the development discussions on Swift Fuel over the last several years, but didn’t realize this option was being pursued. Good to know and hope this comes through for the aviation industry. I don’t believe many pilots can swing the $200 hamburger, let’s keep the $100 hamburger alive folks.

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