xylenes are in 100LL as well as mogas at up to 15%. Lots of nasty stuff in fuels. Where ya gonna draw the line? At least G100UL has gotten rid of the lead, which is known to be highly toxic
 
rocketbob said:
What's enough to cause staining? By significantly increasing the concentrations of these chemicals over whats in 100LL, what will the effect be on paint?
Click to expand...
I'm less concerned about its effect on paint than I am on the fuel system, but your concerns are valid. Xylene is used as adhesive remover and I'm not sure what else. A jump from 15% to 40% Xylene from 100LL to G100UL is concerning to me, although I do trust that GAMI has tested extensively. Are some varieties of ProSeal susceptible to damage by higher Xylene concentration? Viton? Buna-N? Silicones?
 
rocketbob said:
What's enough to cause staining? By significantly increasing the concentrations of these chemicals over whats in 100LL, what will the effect be on paint?
Click to expand...
I believe that the staining is caused by the aromatic amine in the formula. Amines are not typically found in fuels. They are reactive and likely more aggressive than typical fuel components.
 
Yea, the GAMI document doesn't really explain what the offending component in G100UL is. Somewhere, I heard/read that: amine component + UV light + time = paint staining. Could be. I'm not nearly enough of a chemist to know.
 
jrs14855 said:
Cleaner and healthier except for the valves. The valves like the lead.
Click to expand...
The jury is still out on that question, especially since the info thus far (UND) has been in relation to the Swift fuel UL94, not G100UL. But yeah...worth paying attention to as the whole unleaded saga unfolds.

Lycoming Engine’s UL94 Valve Seat Recession Investigation Update

WILLIAMSPORT, PA – In June 2023, the University of North Dakota (UND) Aviation program transitioned its fleet from 100LL to use UL94, a 94-octane unleaded fuel. In October, after logging 46,000 hours using UL94, UND identified abnormal valve seat recession in its Lycoming engines. Following a...
www.lycoming.com www.lycoming.com

www.avweb.com

UND Report Details Valve Issues Experienced With Swift Fuels 94UL

University of North Dakota reports on its experience with fleet-wide switch to Swift Fuels 94UL
www.avweb.com www.avweb.com
 
OK It has been a few months now since G100UL became available in California.

Has anyone done their first oil change on the new fuel? Did you notice anything different?
 
PilotjohnS said:
OK It has been a few months now since G100UL became available in California.

Has anyone done their first oil change on the new fuel? Did you notice anything different?
Click to expand...
If the people running G100UL are anything like me, running unleaded mogas or unleaded UL91, it will be a while before anyone has the opportunity to run only unleaded fuel during a full oil change interval. For me, the main difference is the amount of lead reported in the oil analysis. At the home base I have UL91, but when traveling I burn what's available.
 
PilotjohnS said:
OK It has been a few months now since G100UL became available in California.

Has anyone done their first oil change on the new fuel? Did you notice anything different?
Click to expand...
Can't speak to southern CA, but in northern CA.....it hasn't really been that long since the fuel was really truly available, meaning in the airport storage tank and ready to pump into your airplane.....press releases saying it "is commercially available" don't really count. It's been maybe 6-8 weeks, depending on the airport. I know it is actually for sale at Watsonville (KWVI) and Reid Hillview (KRHV).

Personally, I have not tried G100UL. One of these days I will, it just hasn't happened yet.

I did run mostly Swift 94UL for one oil change earlier this year. The only thing I noticed on the subsequent oil analysis report was the lead ppm number was about half as much when compared to 100LL....no reall suprise (again: 1 data point, running mostly UL). The other oil analysis data were not significantly different from prior ones (when running all 100LL). Also, the valve faces and spark plugs looked cleaner. Sorry, this wasn't a full blown valve condition inspection photo shoot....just a quick look to see how much cleaner things were. One last subjective observation was that when checking engine oil level, the oil seemed to take more flight hours to turn "dark". No hard number on how many flight hours it took, and no calibrated eyeball on what "dark" means......just that the oil seemed to be "clean-ish" longer. Operationally, I could not tell any differences in CHT, EGT, fuel flow, etc. either during takeoff or when leaned at altitude (leaned to the beginning of engine roughness, then enrichen slightly). And, just for the record, my engine is a stock carb'd O-360-A1A, 8.5:1 pistons, running Slick LASAR magneto ignition, approx: 1400 hours since new.

I expect that running G100UL won't be that much different as running 94UL....for me. YMMV.
 
From AvWeb:

Cirrus Tells Owners Not To Use Unleaded Fuel​


www.avweb.com

Cirrus Tells Owners Not To Use Unleaded Fuel

Cirrus says it doesn't approve of the use of G100UL or any other unleaded fuel in its SR series aircraft, but G100UL's developer says that position flies in
www.avweb.com www.avweb.com

Statement from Cirrus:
irrus has been engaged in a comprehensive testing and evaluation program of the GAMI G100UL fuel for over a decade, and has been monitoring field experience with GAMI G100UL since November 2024. While some aspects of the initial Cirrus testing of the GAMI G100UL fuel were encouraging, Cirrus has identified specific concerns regarding material compatibility. Lab testing in coordination with FAA representatives and on-aircraft field observations revealed seal degradation when in contact with GAMI G100UL fuel that has resulted in damage to airframe components and could create airworthiness concerns
 
A local pilot who is also an A&P (and has a day job as a Flight Test Engineer) did what appears to be independent testing of G100UL and recorded these three videos which definitely raise some concerns about material compatibility:


My RV-10 is based out of KRHV (one of the CA airports where G100UL is available - we don't have 100LL). I put in 5 gallons a side a couple of months ago soon after it was made available and didn't see any negative effects but for now, I am waiting till the dust settles before going all in on G100UL.
 
Same here. There is too much noise from all the players because I feel each of them want to corner the market on unleaded AVGAS. People who are comfortable to experiment with the new fuel, collect data and let us know. At least for now, we have two very large test results from operators with large fleets of common aircraft and they are not encouraging. I wish the unleaded AVGAS players will present their data in a scientific manner. Every time I listen to these people, they sounded like they are making a used car sales pitch. It does not give me the warm fuzzy confidence feeling.
 
vas4vans said:
A local pilot who is also an A&P (and has a day job as a Flight Test Engineer) did what appears to be independent testing of G100UL and recorded these three videos which definitely raise some concerns about material compatibility:
Click to expand...
fascinating research. Thank you for posting links to the videos!
 
in god we trust, everyone else bring data.
thanks for the testing. guess i'll be gathering more data. before switching to g100ul. if i need to fill up at KRHV, i woul probably mix g100ul w 100ll left in the tanks for emergency ferry to Slo fo 100ll
 
It's really hard to reconcile the years of GAMI testing with the damage shown in these videos. The paint damage is worse than some paint strippers I've used. The most concerning is with the proseal or whatever tank sealant was used. The tests in the video seem like the first place that GAMI would have started before even thinking about a dyno run. Something is very off - I wonder if the formulation has changed.
 
What I find interesting is that we basically have a single individual (George Braly) developing and marketing G100UL. I expected Exxon or Chevron or some MAJOR oil company to develop unleaded aviation fuel. When I see people report damage to paint and fuel tank sealant when using G100UL and then see George respond with his own test results from his personal Cirrus or show paint samples on his workbench, it doesn't give me warm fuzzies.

Where are the big players in all this????
 
This is why we test and get things out in the community. I am sure Gami will figure it out. I trust them to get it right. But i don't trust the swift fuel crowd, because they seemed to have already used questionable practices at osh.
I am looking forward to a tweak to g100ul that makes it the gold standard. This is hard stuff.
 
Gami is a very small company trying to stay afloat in a REALLY big pool. Not sure we will ever get real data and risk assesment from them. They simply don't have enough assets to feel real risk to offset the strong motivation to not fail.

What we need to do is get Flame Master and other similar companies to do interaction testing with their products. They have deeper pockets and will likely respect the risks associated with new fuels. As G100UL begins to become adopted more widely, they have an implied obligation (legally speaking) to tell us if these new fuels are compatible with their products. As consumers, we have a reasonable expectation to assume compatibility (i.e. to a non-chemist, "fuel is fuel") and therefore up to them to tell us If G100 has the potential to soften and compromise Proseal. They are staring at significant legal risk if they do nothing. Maybe we should be tryying to recruit their efforts. I would trust Flame masters research on this, as they have a lot to lose. Not much sense recruiting the paint makers, as the legal risks are MUCH more limited. Not their issue if you allow agressive chemicals to attack their paint. And they rarely promise their paint is resistant to fuel.

If flame master comes out and says G100 will destroy proseal integrity, THAT IS IT. FAA will stop this dead in its tracks!
 
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vas4vans said:
A local pilot who is also an A&P (and has a day job as a Flight Test Engineer) did what appears to be independent testing of G100UL and recorded these three videos which definitely raise some concerns about material compatibility:


My RV-10 is based out of KRHV (one of the CA airports where G100UL is available - we don't have 100LL). I put in 5 gallons a side a couple of months ago soon after it was made available and didn't see any negative effects but for now, I am waiting till the dust settles before going all in on G100UL.
Click to expand...

Video #4 from Mike Luvara:

 
Offering no TEL AvGas or Dial-A-TEL dispensing is really the answer. The aromatics of zero ethanol Mogas and G100UL are NOT optimal, even IF meeting our octane needs. Xylene and M Toluidine are raising the hair on my neck.
 
🤷‍♂️
Lycoming publishes specifications for approved fuels in Service Instruction 1070. G100UL is not listed as an approved fuel in Service Instruction 1070.

Learn More About Lycoming’s Efforts Around Unleaded Fuels

Lycoming Engines has been producing piston aviation engines for over 95 years, and we “build every engine as though we were going to fly it ourself!” Safety is an utmost priority, and we strongly support efforts to eliminate lead from aviation fuels. For this reason, Lycoming has been...
www.lycoming.com www.lycoming.com
 
moosepileit said:
Dial-A-TEL dispensing
Click to expand...
Neat idea but I'm doubtful it'll ever happen. Equipment costs plus TEL is liquid concentrated brain damage and is extremely difficult to transport and handle safely.

Removing the TEL and making a lower octane unleaded avgas would be nice, but from what I've read, the majority of the avgas is used up by the fleet that needs the higher octane. Hence the alternate formulations.
 
ve0kog said:
🤷‍♂️
Lycoming publishes specifications for approved fuels in Service Instruction 1070. G100UL is not listed as an approved fuel in Service Instruction 1070.

Learn More About Lycoming’s Efforts Around Unleaded Fuels

Lycoming Engines has been producing piston aviation engines for over 95 years, and we “build every engine as though we were going to fly it ourself!” Safety is an utmost priority, and we strongly support efforts to eliminate lead from aviation fuels. For this reason, Lycoming has been...
www.lycoming.com www.lycoming.com
Click to expand...
I am surprise GAMI doesn't allow Lycoming to officially test its fuel, and doesn't provide the technical information of the fuel to Lycoming.
 
PhatRV said:
I am surprise GAMI doesn't allow Lycoming to officially test its fuel, and doesn't provide the technical information of the fuel to Lycoming.
Click to expand...
Not really surprifing IF they already suspect compatibility issues. Better to release it into the wild and then blame age and poor maintenance practices :-) After all these years of testing, I find it hard to believe that GAMI doesn't know about the affect on paint and proseal. Not throwing stones at GAMI, but one has to wonder. The fact that they immediately blame the owners and mechanics vs saying "good catch" and testing is highly suspicious behavior. A top flite outfit would undergo independant lab testing to prove that it is not their fuel causing issues. The videos in this thread give some clues as to why that may not be happening.
 
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Walt said:
PPG Aerospace likely sells way more fuel tank sealant than FM.
Click to expand...
I really wanted G100UL to work out. But I've been concerned for a long time that the octane enhancing chemistry of an alternative might be just as bad or worse than lead for people to be around. Aromatic hydrocarbons - benzene, xylene, toluene, etc are really really nasty chemicals that cause cancer and other problems if you just look at them sideways. I suppose the environmental impacts are less because they get burned up. But really not safe to handle or be around. So I was resigned to the idea that some degree of PPE and care in dispensing would be needed as an acceptable trade-off for eliminating the lead. The big payoff is that our engines would be so much happier.

But now, seeing Mike's video of the brown goo dripping out is the last straw.

Any fuel that creates brown goo when it evaporates will be a disaster for a carburetor if you let fuel sit in it for a few months. (Another test for Mike Luvara to do?)

I think it is sad for George Braly who has really dedicated himself to getting a solution. I really wanted him to succeed. But for all the testing and advocating, I am really surprised that he didn't do compatibility testing, or he did and withheld the results. An attitude such as, "well, sure it attacks Buna-N/nitrile rubber, so you just need to upgrade all your o-rings to Viton" is sadly just not practical. There are seals in places you can not really get to, or wouldn't know they are there, until it is too late.

The problem for GAMI now is that he is so far in on this formulation that he can't say, "oh darn, back to the drawing board to make a formulation that is compatible with old airplanes". So denial/deflection will be his only option until the evidence is just too convincing.

Also frustratingly, there may not be a feasible solution -- it may be that any/all organic octane-enhancing chemicals will be incompatible with traditional elastomers used in aircraft systems.
 
After the self induced stress of building my fuel tanks, there is no way I'm putting G100UL in my tanks unless I'm 100% sure it won't damage the tank sealant. I'm glad I'm at least 18 months out from finishing my build so this issue has time to shake out. Then again, we may end up repeating this with an alternative UL fuel.

BTW, watching the gaskets swell in that video in G100UL (but not in 100LL) was a little unnerving...
 
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Some data points, you determine the value.

My 6a was built in 1991, all original airframe/tanks still
I fly 100+ hrs a year
Purchased 7 yrs ago with 733 TT engine airframe 1664 TT today
0320 D1A new 1991
Most all fuel, oil lines standard rubber of sorts 2018 all new
I run close to WOT LOP ( says the EGT) 4-8K feet
I have run 91-93 octane UL alcohol free exclusively 7 years
I don’t have leaking tanks
I don’t have/unaware (healthcare work-life) of any medical issues
I don’t have leaking fuel lines/carb
My plugs are really clean , mag check 20 rpm drop
My paint shines great, no clear coat either
I save $100s a year in fuel cost $3.84 gal today
It does REALLY STINK, I keep it off my skin, mainly due to odor
 
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scsmith said:
Also frustratingly, there may not be a feasible solution -- it may be that any/all organic octane-enhancing chemicals will be incompatible with traditional elastomers used in aircraft systems.
Click to expand...

The solution is long, slow, and painful. Tradition (and regulatory capture) is the problem.

High compression and turbocharged engines that run on less problematic unleaded fuels exist in just about every other application of the ICE and are gaining ground in aviation.
 
Ok time to keep 100ll and tweak g100ul and start retesting, like a large petroQ company would be doing as basic research suggests. G100ul is closebut needs one more tweak?
 
RV8JD said:
GAMI Chief of Engineering George Braly has said the issues with some aircraft can be traced to maintenance or aircraft age issues.
​
Click to expand...
Would the aircraft have these issues with 100LL? If yes then fine, if no then that’s a problem for “aircraft age” . The majority of the fleet are aging aircraft.

New fuel without lead 👍🏻 but only good if your aircraft is brand new 🤣🤣🤣

Doesn’t seem like it’s compatible or drop in
 
N8DAV8R said:
The solution is long, slow, and painful. Tradition (and regulatory capture) is the problem.

High compression and turbocharged engines that run on less problematic unleaded fuels exist in just about every other application of the ICE and are gaining ground in aviation.
Click to expand...
Yeah it is really sad how the faa has dealt with this. Swift 94 is a viable solution for a very large chunk of the fleet. Force the fbos to offer it and put a $2 premium on 100ll. Majority of problem solved. Jusy follow the cigarette model. Raise the taxes high enough and nobody uses it anymore. We can use sharp minds like braly to develop knock sensing technology to more safely use these fuels.
 
In my reading of the judges tentative ruling yesterday on the California Motion to Enforce and Modify Consent Judgment;
filed by Center for Environmental Health, I feel the judge understands the issue much better than I expected. It is a very complicated issue between, chemical engineering, product distribution, OEMs, and government regulation. Seems like his ruling is based on the legal definition of what the consent decree says, as it should be.
 
lr172 said:
Swift 94 is a viable solution for a very large chunk of the fleet. Force the fbos to offer it and put a $2 premium on 100ll.
Click to expand...
How about keeping 100LL the same price & discount the new non-lead blends.
A few years ago I was willing to try swift. It was offered at Lakeland. It was a higher price than LL.

Try a new blend with unknown results at a higher price? I don’t think so. No Thanks.
 
roadrunner20 said:
How about keeping 100LL the same price & discount the new non-lead blends.
A few years ago I was willing to try swift. It was offered at Lakeland. It was a higher price than LL.

Try a new blend with unknown results at a higher price? I don’t think so. No Thanks.
Click to expand...
Sadly, whatever we get is going to be more expensive than 100LL and due to the lead, we are living on borrowed time IMHO. The california stuff is just the tip of the iceberg. I really wish we could also get access to Mogas, even with ethanol. Would be more than happy to retrofit for compatability. It is way cheaper and a MUCH better long term option. Just too many issues for wide spread usage. The reality is that we would be far better off in the long run doing what was necessary to equip and relearn to use lower octane fuels. However, too many will complain and you end up with what is going on with G100.

On a side note, this whole issue really makes me question whether we can ever find a suitable 100 octane replacement. The G100 thing has always scarred me due to the forever GAMI royalty. This is already boutique fuel and one more layer of markup hurts.
 
Remember when gas cans were simply devices that held gas? Then came California and their C.A.R.B. Now gas cans cost twice what they should and have an mechanism that makes them pour slow and crappy. I’ve spilled more fuel using it than any vapors it’s preventing.

Rest assured CA will have like minded states join them to drive this G100 nonsense.

It’s all win win for them. If G100 is bad for aircraft and the aircraft go away (faster option) or it’s OK-ish and adds so much cost that aircraft go away (slower option). Then the city planners can take the land and increase the tax base.

Why can’t we get 93 no ethanol MOGAS? Because the aircraft that need 100 are the overall volume buyers. The remaining few don’t matter from a cost benefit perspective.

Imagine a world where we didn’t turn food into ethanol and mandate it be 10% of our fuel. We’d just go to the pump and bring it to the hangar. Or it could be easily delivered to the airport since it’s not a rarity. I chose 8.5:1 So I can run 93 per Lycoming, Never saw the benefit of hi comp just to get a few HP.

What’s more disheartening is the new price tags on engines that may become boat anchors if the fuel issue continues to be handled by bureaucrats.
 
lr172 said:
Sadly, whatever we get is going to be more expensive than 100LL and due to the lead, we are living on borrowed time IMHO. The california stuff is just the tip of the iceberg. I really wish we could also get access to Mogas, even with ethanol.

On a side note, this whole issue really makes me question whether we can ever find a suitable 100 octane replacement.
Click to expand...
There's basically 2 problems to solve.

1. Maintain detonation margin for high compression or forced induction engines.
2. Maintain compatibility with legacy GA fleet fuel systems (rubber).

The bureaucratic solution is to develop a blend of chemicals that is far more expensive, toxic, dangerous, and environmentally damaging then lead. And force you to use it.

A better solution would be to use ethanol, which any refinery can blend and ship much cheaper than the current 100ll (And cheaper still without fed and state road tax). Then remove the STC bureaucracy to make retrofit fuel systems affordable.

The right solution is to quit scaremongering and over stating the danger of leaded fuel. And remove the STC bureaucracy to make retrofit fuel systems affordable. This would let the market decide (how America is supposed to work).
 
I found this comment from the judge interesting and positive:

"CEH has not demonstrated that there will be significant demand from consumers for G100UL fuel until it has been reviewed by PAFI, meets an ASTM Standard, has been peer reviewed, and GAMI has addressed concerns such as whether it degrades tank sealant."

Clearly he paid attention to the details and is not going to let these folks slip in onerous mandates until the real work has been done. Not good for GAMI, as the stage has been set for requiring them to address the issues outlined in this thread. Chalk up a win for the consumer here. These wins seem to be more and more rare the older I get.
 
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