Auto Gas STC Pros and Cons

airbusflyboy

Wanted to see how many folks are using auto gas STC in their aircraft ? I don't believe it is very easy to find MOGAS anywhere anymore ........ What does it cost to get a autogas STC ?

Scott Sherer

Good questions. I've never actually looked into the autogas STC but here's the link. https://www.autofuelstc.com/ .I'm reading now and I've discovered that turbo charged engines are not covered by the STC, which leaves my turbo Arrow out. But there are lots of airplanes and engines that are covered. I ran a couple of engine samples and it looks like the STC is about $3,000. Thanks for asking.

arrow76r

When I had a C-172, Continental O-300, I had the EAA STC for auto fuel. I had A LOT of trouble with it! Vapor lock was insidious resulting in total engine stoppage after landing and just beginning to taxi in hot weather. When hot, the engine wouldn't start either. So I ended up with 100LL in one tank and autogas in the other and ONLY used the autogas in flight. Got to be a real pain. Plus the spark plugs would foul quickly. I only used it for a short time as a result. That was in the days before ethanol was mandated by the feds for autogas too. Nowadays I wouldn't touch it!!!

Scott Sherer

Thanks for your comments, Jim. I'm wondering if others will post their experiences. This is new for me.

arrow76r

The ethanol in autogas is known to be bad on rubber components in fuel lines, etc. It also has nowhere near the "shelf-life" of avgas resulting in deposits in the fuel systems and gumming up things after long periods of storage. Obtaining ethanol free gas is tough unless you are located in, or close to, farming areas where one could buy "normal" gas for "off-road, non-taxable" uses such as in farm equipment. Plus the fuss and bother of dragging 5 gallon cans to the airport, potentially dinging the wings, etc. makes this (to me at least) a non-starter even if my Arrow could use that gas but since it requires 100 octane fuel (like yours, Scott) it is a moot point. IMHO, leave that gas for cars and Rotax engines!

Scott Sherer

Great comments, Jim. Thanks so much!

Harley Kleemann

No fuel injected aircraft engine can use mogas...nor would I want to in my Arrow. Like Jim stated, it's a pain in the butt!

Don3950

I ran MOGAS in my 140 with the Peterson STC. Actually, there are 2 STC’s, one for the engine and one for the airframe. Basically just paperwork.

MOGAS is the same as “Rec Fuel” that you can get at most gas stations nowadays. It contains no ethanol and is safe for most lower HP carbureted engines that were designed to run on 80 octane. I would run some 100LL every once in a while or just blend the 2 fuels. I had no problems at all with it.

As was already mentioned you have to weigh the cost per gallon savings to having to bring 5 gallon cans to the plane. For me it was a good deal.

Scott Sherer

Thanks for your comments, Don.

jimcurns

I used mo gas for 10 years in a Cessna 150 with no issues at all. Probably averaging 70% mo gas to 30% 100LL. Many in the know said that's about an ideal average blend of fuel and lead for that engine. Fast forward to my Cherokee 180 and I have not used it, not that I'm a purist. I don't have the STC, but that isn't my concern. The PRC that seals the tanks has, at my airport, received a reputation for causing tank leaks. I'm not so sure I believe that, and wonder if others here would know more about that. My source at that airport has always hated mo gas and profited from 100LL. Still I pause to wonder.

Do I use ethanol gas in other stuff, yep with the understanding that shelf life is indeed shorter. I grow corn for part of my living and to be quite honest we growers get a bit tired of the ethanol bashing we often here that a guys' brothers buddy's mechanic said. Use what you wish, it's a free country. But understand a few things about it. The oil industry hates the competition and loves to propagate reasons not to use it. They sold MTBE as an octane enhancer, which worked great, and was cost effective except it was practically poison and was banned in most areas. Ethanol which eventually took 10% market share from the oil industry and was kinda shoved down their throat causing a lot of backlash was renewable, healthier, and sustainable. It too had a few faults. One is the shorter shelf life, and the other was a seal issue. The seal thing depends a lot on what you use to start with. Older seals will after all fail at some point but often the fuel was blamed instead of old seals. Newer seals have made a significant difference from what many in the industry tell me and seal failures are no longer common.

There is far more to this issue I would rather not debate. I understand the comments about ethanol are well intentioned, as are mine. As with most things in life, this issue has a lot of "it depends" that goes with it. Use what you like, there is room for varied opinions.

Jim

arrow76r

Thanks for the info, Jim! It is good to hear from one on the "supply" side of the story. I do remember MOGAS pumps indicating that MTBE was added but I had not noticed its disappearance! A lot of the issues I had with my 172 could be the altitude here. My field elevation is just about 6900 feet and that probably contributed to the fuel vapor pressure problems I had.

airbusflyboy

Thank you guys !!! I believe the Petersen STC used to be a dollar a horsepower but prolly that has doubled by now? What has happened to SWIFT FUEL ? There was rumors going around that it was going to be less cost than 100LL but I don't know if it ever came to market and where in the market ? I once bought a Piper Shortwing that had been sitting for a long time out of annual, unfortunate it was left there with Ethanol laced auto fuel, the resultant mess was dried up fuel in the fuel lines and our efforts to revive the aircraft was abandoned, sold it as a project to an A&P that was able to get the mess cleared up on his own time. Another guy at my airport, M72, years ago had left his PIper Colt fuel tanks full of ethanol laced auto gas, and it ate right through the rubber hose connector lines in the wings and flowed down the sides of his Colt , the resultant mess was a pile of melted paint on the floor below his aircraft. MOGAS was a excellent alternative to 100LL as it was cheaper and the aircraft engines that only required a lower octane operated more efficiently. 100LL fuel is four times the lead content of auto gas/mogas.

Scott Sherer

Wow, those are interesting stories. Isn't technology wonderful