G100UL

Posted by No-Collar-1643@reddit | flying | View on Reddit | 14 comments

Hey y’all, I have a Cessna 150 and a local airport is getting G 100 unleaded and is very pushy about getting people to come and start using their fuel. So much so that they are even giving me a free STC. I run a mix of Mo gas and 100 low lead and have an STC for the mix. feel that the two provide good economy and performance together. G 100 unleaded is almost twice the cost of unleaded ethanol free Mo gas. so I would only be doing it for an added performance and reduced maintenance cost, if even that is a thing. For those who don’t know, the Cessna 150s sports a Continental 0-200-a. mine was overhauled in the 90s, so I highly doubt it has hardened valve seats. I haven’t heard much news regarding the subject matter within the last two years. Is it magic pixie dust that reduces Maintenance costs, or is it going to put me in a field?

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14 Comments

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AWACS_Bandog@reddit

One of these days, id love to see a 100UL get adopted. From everything ive seen of GAMI, this isn't it, not by a mile.

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zero_xmas_valentine@reddit

No experience with G100UL specifically, but my home field has UL94 (Swift) and I've been loving it. I put Swift in my right tank and 100LL in my left tank if I have time, and then run my taxiing on the right tank so I don't foul the mags up at low RPM. Maybe I'm overthinking it but it's been solid. Also on an O-200 FWIW.

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mustang__1@reddit

We changed our plugs (TSIO-520) and stopped having fouling issues. YMMV...

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zero_xmas_valentine@reddit

I'm guessing that's a separate issue. O-200s are notorious for being lead magnets on the ground, they just don't run hot enough.

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No-Collar-1643@reddit (OP)

That's very interesting! How many hours and what's the age of your engine? Have you had enough time with the fuel to observe any changes? Any oil analysis or compression checks done? Sorry for the question blast; I am just really interested in any additional details you may have

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zero_xmas_valentine@reddit

Very old engine, I'm past TBO. Fuel economy doesn't change by enough to notice. Compressions are normal (mid 60s, which on a Continental is more or less what you're gonna get). Oil analysis looked great last year, still waiting on the one from this year, but no metal where it shouldn't be. I can't remember which brand of analysis we used. AeroLabs maybe? But all the parameters were green other than one or two yellows, and it's a very very old engine so that doesn't surprise or overly concern me.

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SSMDive@reddit

There is a battle being waged online right now. Two very vocal camps. One claims George Braley is a god and anything Gami does is the best thing ever. The other camp seems to claim that the only thing that will ever work for aviation is 100LL and anything against that is some "green new deal" BS.... Both are likely wrong. The truth is that if someone offered me a free STC for G100UL, I'd likely take it. But there is no way in hell I'd actually put it in my plane at this early of a point. There are some credible reports that G100UL is eating paint, causing fuel leaks, and messes with O rings. The "George is a god" crowd all claim the leaks were there, your MX is crap, and your paint was already bad you were just to stupid and lazy to notice. The "G100UL is the devil" crowd all point to it and claim we are all gonna die. Me... I tend to think that there likely is something to the claim that new product made with the same chemicals as paint stripper in higher does than the 100LL you are currently using could cause problems. So there is no way in hell I will be using it anytime soon. Here is some A&P that I know nothing about, but his testing methods seem decent and to me seem to show a problem. There are 4 parts (IIRC) and he answers some testing issues he had in part 1. I find his data compelling and feel G100UL does contribute to some of the issues the people are claiming. Watch the videos and make your own choice. [https://www.youtube.com/watch?v=sPeQ6T3vB2E](https://www.youtube.com/watch?v=sPeQ6T3vB2E) People claimed "We don't know the type of paint"... So he took samples from several panels and treated them the same - 100LL had no issue, G100UL had issues. He then took a piece that was painted in Jet Glow and cut it in half. The 100LL had no issues, the G100UL had issues. He then took pieces from a freshly painted Pitts experimental that they knew the paint and again, the 100LL didn't have any issues and the G100UL did. He took O rings and soaked them and again 100LL no issues, G100UL had issues. Same with "Fuel Lube".... I found his testing interesting and it has convinced me NOT to use G100UL at this point. I have no issue with GAMI and I'd like a lead free gas... I am not willing to be an early adopter and risk having it wreak my fuel system and paint.... My personal opinion is it is causing issues and I am not willing to be a tester based on the risk.

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Any_Subject_2966@reddit

I would not even consider using this fuel unless it was way cheaper than the tried and true blue stuff. Why would I? What’s my incentive? Hopefully this new administration will grandfather in 100LL for good and we can put all this unleaded fuel stuff to bed. There will never be an unleaded fuel as good as 100LL. if they could do it it would have been done decades ago. Compromises will be made, I am convinced of that. The stuff you have to do to unleaded fuel to make it perform like leaded compromises other qualities of the fuel.

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redditburner_5000@reddit

I'd stick with mogas and just lean appropriately. In my experience, mixing fuels does not somehow make it better or worse. The school I CFI'd for used mogas exclusively. Engines would run past 3000hrs regularly. Run what you can as economically as you can. I'd just do mogas and get good at using the red knob and carb heat. That's me though. I see no operational advantage in going with a fuel that costs 2x as much as 100LL if I could get pure 87. I've not noticed a difference in performance between 87 and 100LL in Champs, 150s, 172s, Cherokees, or Apaches.

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SSMDive@reddit

There is some guidance from Rotax suggesting to mix 100LL and Rec90. Rec90 alone has been known to have vapor lock issues. We learned this because a buddy flew a XC and when leaving on takeoff his engine started to act like it was vapor locking. He looked into it and we finally gave up and drove a trailer up and pulled the wings off the RV12 and drove it home. After looking through the engine we could find no issues. Called Rotax on Monday and were told that pure Rec90 could be an issue. Started mixing a little 100LL into the Rec90 and never had that issue again.

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youngbus1141@reddit

The Vans RV12 (Rotax) crowd strongly recommends mixing unleaded and 100LL to combat RVP issues. Winter mixes are way too volatile for early summer at altitude.

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No-Collar-1643@reddit (OP)

I appreciate your personal experience, I think I'll do just that. Thanks!

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noahhl@reddit

There have been a lot of reports about G100UL destroying paint, o-rings, sealants, etc. GAMI denies that anything unusual is happening, but a look at a variety of forums will find a lot of unhappy people who tried G100UL and regret it. I'm one of the biggest boosters of unleaded fuels out there, both for engine and environmental health, but I wouldn't put G100UL in my plane if it showed up at my field tomorrow until there's more clarity around material compatibility. Especially if you have mogas available on field or have already figured out the logistics of using it, I'd stick with that.

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rFlyingTower@reddit

This is a copy of the original post body for posterity: --- Hey y’all, I have a Cessna 150 and a local airport is getting G 100 unleaded and is very pushy about getting people to come and start using their fuel. So much so that they are even giving me a free STC. I run a mix of Mo gas and 100 low lead and have an STC for the mix. feel that the two provide good economy and performance together. G 100 unleaded is almost twice the cost of unleaded ethanol free Mo gas. so I would only be doing it for an added performance and reduced maintenance cost, if even that is a thing. For those who don’t know, the Cessna 150s sports a Continental 0-200-a. mine was overhauled in the 90s, so I highly doubt it has hardened valve seats. I haven’t heard much news regarding the subject matter within the last two years. Is it magic pixie dust that reduces Maintenance costs, or is it going to put me in a field? --- Please downvote this comment until it collapses. --- I am a bot, and this action was performed automatically. If you have any questions, please [contact the mods of this subreddit](https://www.reddit.com/message/compose?to=/r/flying).