FAA Approves 100R Avgas in Cessna 172s

[MikeOH]

9 minutes ago, redbaron1982 said:

But a new standard would need to be defined, right? the TCDS calls for 100LL, which in turn have a minimum TEL content. So you cannot have UL meet the 100LL standard.

I can't speak for all TCDS, but a quick look at the TCDS for Mooney shows that's NOT the case for most models (the Porsche Mooney does limit fuel to 100LL, however):

 

[Marc_B]

There is plenty of information that GAMI presents in a very open fashion...i.e. detonation data for Swift UL94.  But there are lots of data that GAMi intentionally doesn't release.  I don't think that we'll ever see the data that the FAA used to validate a blanket inclusion of every airframe on the STC AML.  It's easier for me to extrapolate what "boundary" testing looks like for engine data for the engine STC AML as there aren't many manufacturers that are reflected in those engines and there are more similarities than differences.

But for the airframes...that's an entirely different story.  I suspect GAMI didn't know what they didn't know.  Meaning I don't think they anticipated having escalated issues with roll out that they've wound up having.  Even with the Cirrus that had issues, they're baffled that they have one Cirrus using the fuel for "15 years" and can't imagine other aircraft having any issues.  Personally I think this is because the "boundaries" tested for the airframes did not actually identify all of the boundaries.  But this points to the flaw in the STC system for use of blanket fleet fuel approval...a manufacturer creates the data, creates the testing protocols, performs all the testing, and submits data to the FAA for them to stamp.

In my mind, if you are applying a STC to an airframe/engine...why should that not have required testing for that equipment??

...imagine how our pharmaceutical and medical industry would look if that's the case with medicine???  ...oh wait, it's called an emergency use authorization.  i.e. government feels this is important enough that we shortcut validation testing and streamline approval.  The idea is that the FAA accepts the risks, and hopes that the details finally come out in the wash to see if this should be continued or not.

[Marc_B]

@MikeOH I've always been told that the 100/130 wasn't specifying a category of fuel meeting that octane but rather was specifying a specific version of leaded fuel that was 100/130 green AVGAS.  Do you know if that's the case with the TCDS? 

i.e. one of the questions I originally posed to Mr. Braly when he presented to the Colorado Pilot's Association was why did GAMI need a different fuel placard when my aircraft already has a placard that says 100LL or 100 octane min fuel?  His answer was that they felt that specified a particular fuel and wasn't applicable.  Although I always thought that this was the way that the FAA could apply a fuel going though PAFI/EAGLE with fleet authorization by including said fuel under the "100 octane min aviation fuel" approval.

Of course moving into the era of potentially selling fuels that aren't fungible (i.e. 100R prohibits use of G100UL), the specifics of what fuels you are approved for and using will probably be more important.

[MikeOH]

2 minutes ago, Marc_B said:

@MikeOH I've always been told that the 100/130 wasn't specifying a category of fuel meeting that octane but rather was specifying a specific version of leaded fuel that was 100/130 green AVGAS.  Do you know if that's the case with the TCDS? 

i.e. one of the questions I originally posed to Mr. Braly when he presented to the Colorado Pilot's Association was why did GAMI need a different fuel placard when my aircraft already has a placard that says 100LL or 100 octane min fuel?  His answer was that they felt that specified a particular fuel and wasn't applicable.  Although I always thought that this was the way that the FAA could apply a fuel going though PAFI/EAGLE with fleet authorization by including said fuel under the "100 octane min aviation fuel" approval.

No, I do not know. Looking at the TCDS, the F model was certified back in 1966 when 100/130 was the standard and 100LL was not even available, while the V model was 2017 when 100/130 really wasn't available so a 'generic' 100 octane was included so the approved fuel was NOT limited to only 100LL.  My question would be if generic 100 octane would meet the 100/130 ASTM standard from 1966?  If so, it would be rational to conclude they were interchangeable; i.e. the FAA would approve equivalence if questioned.

[Pinecone]

On 6/5/2025 at 11:16 AM, EricJ said:

STCs for fuels that are ultimately compliant to an ASTM standard will likely become a non-issue, which I'm guessing is likely the intent.   In other words, until the ASTM standard is finalized the fuels can be used via the STC.    Once the ASTM compliance is in place and established, then I don't know what would stop somebody from just pointing at their TCDS and saying they're using a compliant fuel if the fuel is marked as 100 grade aviation fuel.    I suspect this is the overall plan for those pursuing ASTM standardization.   That seems to be a big reason to pursue that.

An ASTM standard only means that the fuel meets some specification of that makes it up.  It does not have or mean that that fuel is safe for paint or that it even safe for engines.

GAMI could have done an ASTM standard and it would be THE SAME FUEL AS IT IS NOW.

ASTM only sets a standard to say that any product is the same as another product.

You could do an ASTM spec for sweet tea if you wanted to.

[Marc_B]

@Pinecone I think you're looking at it though the eyes of GAMI who says "our spec is better than ASTM."  The issue is having an open industry standard for fuel, a means of testing, and a QA process from blend, distribution, and sale.  Every step in the pathway has method to verify fuel.  Unfortunately with G100UL there is only one company that can do that and it's GAMI.  So from their standpoint they say "our spec is similar to ASTM, looks like ASTM," but we're the only one who can test, verify, and certify conformance.

So with all the fuel issues in California, who has the ability to test/certify that the G100UL was conforming?  Only GAMI.  Not the FBO, not Vitol, not the end-users, certainly not anyone in the aviation industry.  They don't have a fuel spec, it's proprietary trade secret.  Mr. Braly won't even divulge the aromatic content.  A DHA is performed on each batch, but isn't included with the certification by design.

There needs to be an industry standard, that is field validated and testable by the industry.  The ironic thing is that GAMI built their "spec" around ASTM, using ASTM tests, to look like an ASTM certification, but don't want to use ASTM certification?

What third party is able validate fuel if GAMI is unwilling or unable to do so?  Who establishes the standards, quality, and safety of G100UL through each step of the process from blending through distribution to sale?

[EricJ]

5 hours ago, Pinecone said:

An ASTM standard only means that the fuel meets some specification of that makes it up.  It does not have or mean that that fuel is safe for paint or that it even safe for engines.

GAMI could have done an ASTM standard and it would be THE SAME FUEL AS IT IS NOW.

ASTM only sets a standard to say that any product is the same as another product.

You could do an ASTM spec for sweet tea if you wanted to.

Many standards, like ASTM, are collaborative industry standards.   They are generally not written by a single company, but in a consensus process involving many industry stakeholders/players.   GAMI could not have "done an ASTM standard" without being subject to the scrutiny and give-and-take of a typical industry standard process.   It appears that this is why they opted out of that process.   It is highly unlikely that any ASTM standard would have resulted in what G100UL is now or vice versa.   That's not how standards work.

 

[MikeOH]

Just throwing out another question that's been rattling around in my head:

What is the shelf life of G100UL compared to 100LL?

As I understand it, Braly brewed up on the order of a million gallons of G100UL which is how old, now?  If only 10,000 gallons have been sold, and sales aren't escalating, how old will the last gallon of G100UL be when it is finally sold?

Tell me why that shouldn't be a concern?

[Hank]

Because George says so???

Bet he won't share any data to support his "nothing to see here" position.

[Pinecone]

On 6/6/2025 at 4:20 PM, Marc_B said:

@Pinecone I think you're looking at it though the eyes of GAMI who says "our spec is better than ASTM."  The issue is having an open industry standard for fuel, a means of testing, and a QA process from blend, distribution, and sale.  Every step in the pathway has method to verify fuel.  Unfortunately with G100UL there is only one company that can do that and it's GAMI.  So from their standpoint they say "our spec is similar to ASTM, looks like ASTM," but we're the only one who can test, verify, and certify conformance.

So with all the fuel issues in California, who has the ability to test/certify that the G100UL was conforming?  Only GAMI.  Not the FBO, not Vitol, not the end-users, certainly not anyone in the aviation industry.  They don't have a fuel spec, it's proprietary trade secret.  Mr. Braly won't even divulge the aromatic content.  A DHA is performed on each batch, but isn't included with the certification by design.

There needs to be an industry standard, that is field validated and testable by the industry.  The ironic thing is that GAMI built their "spec" around ASTM, using ASTM tests, to look like an ASTM certification, but don't want to use ASTM certification?

What third party is able validate fuel if GAMI is unwilling or unable to do so?  Who establishes the standards, quality, and safety of G100UL through each step of the process from blending through distribution to sale?

Vitol can test, as they know what they put into the tank, so have the formula.

Why have an ASTM standard for a single product?   ASTM is so that you can make the same product as me and the end user knows that they should be functionally the same.

If there was an ASTM standard for Sweet Tea it would specify a range of sugar.  That would cover mildly sweet to very sweet.  So that people buying your ASTM Sweet Tea would know it is within that range.  But there would be no ASTM standard for Coke, as that is a specific formula that makes a single product.  No one else can make Coke unless licensed by Coke.

G100UL is a specific blend.  Not a range of possible blends to sort of be the same.  The only benefit of an ASTM standard is that everyone would now know the formula for their product.  So, like Coke, there is no benefit to the THEM.

 

[Marc_B]

1 hour ago, Pinecone said:

Why have an ASTM standard for a single product? 

Simply because it's not going to be a single FBO, single distributor, single transport, etc.  GAMI isn't a part of the AVGAS fuel pathway and never intended to touch a single component of it.  Coca-Cola controls all the supply and distribution lines of their product.  GAMI isn't Coca-Cola.

[redbaron1982]

Nice to see Swift fuel going international already.

https://www.travelandtourworld.com/news/article/antwerp-airport-leads-the-bold-charge-toward-eco-friendly-aviation-with-historic-debut-of-swift-100r-unleaded-fuel-marking-a-transformative-step-for-sustainable-flight-new-updates-you-need-to-know/

[IvanP]

1 hour ago, Marc_B said:

 GAMI isn't Coca-Cola.

They would very much like to be  This is all money grab - get your proprietary single-source fuel mandated by the govt and you have a license to print money in form of a govt sanctioned monopoly. 

Edited June 9 by IvanP

[Pinecone]

2 hours ago, Marc_B said:

Simply because it's not going to be a single FBO, single distributor, single transport, etc.  GAMI isn't a part of the AVGAS fuel pathway and never intended to touch a single component of it.  Coca-Cola controls all the supply and distribution lines of their product.  GAMI isn't Coca-Cola.

ASTM doesn't either.   

How does a standard that deals with making the product cover all those things???

[Marc_B]

"ASTM's petroleum standards are instrumental in the evaluation and assessment of the physical, mechanical, rheological, thermal, and chemical properties of crude oils, lubricating grease, automobile and aviation gasoline, hydrocarbons, and other naturally occurring energy resources used for various industrial applications. These fuels are tested for their composition, purity, density, miscibility and compatibility with other fluids and materials, toxicity, and thermal stability among others. These petroleum standards allow petroleum refineries, automotive and aviation companies, and other geological and chemical processing plants to appropriately examine and process these fuel oils ensure their quality towards safe and efficient use."

In fact, GAMI DOES use some ASTM standards, they just don't want to define their fuel to ASTM (or anyone else).  Having an OPEN standard that can be tested by others I think is VERY important.  Who can confirm conformance of the product outside of GAMI?  Vitol can only compare field and distribution use to their original mix...but they cannot say if it is conforming or not unless it's identical to the product they sold.  Per GAMI documentation, the detailed hydrocarbon analysis is shared only with GAMI.

@Pinecone Additionally, G100UL isn't a specific blend like you mentioned because by it's nature it's marketed as completely fungible with any percentage of 100LL and still be listed as "conforming G100UL."  So it IS actually a range of potential blends even if the original recipe is exact (which it likely isn't which is why each DHA is a blueprint for origination).

[EricJ]

24 minutes ago, Pinecone said:

ASTM doesn't either.   

How does a standard that deals with making the product cover all those things???

Our local self-serve fuel vendor is very diligent about testing a fuel delivery to the spec before it goes in their tank.   I've been there when they've been processing a delivery.   It's impressive.   The guy delivering the tank was totally on top of it, too.   They're all involved in verifying the spec is met all the way through the supply chain.   It's one of the reasons consensus standards involve stakeholders from all parts of the chain, which helps make deployments successful and avoid surprises.

[1980Mooney]

4 hours ago, IvanP said:

They would very much like to be  This is all money grab - get your proprietary single-source fuel mandated by the govt and you have a license to print money in form of a govt sanctioned monopoly. 

I’m not sure if I follow your point. Swift also requires that you pay for an STC to use their fuel.  And the economic reality is that, because AVGAS consumption is so low,  virtually all but the busiest airports have only one supplier of AVGAS. 

- Daily deliveries of all grades of AVGAS average slightly over 400,000 gallon per day NATIONWIDE. 

- There are about 5,000 public airports and 14,000 private airstrips. 
-  Just considering the public airports, that is ONLY 80 gallons per day per airport on average. 
 

Gas/connivence store sell more beer than that per day.  Grocery stores sell more milk than that per day. 
 

You may want market competition but the market reality does not support it. The Govt doesn’t have anything to do with it. 

Edited June 9 by 1980Mooney

[Pinecone]

3 hours ago, Marc_B said:

 

@Pinecone Additionally, G100UL isn't a specific blend like you mentioned because by it's nature it's marketed as completely fungible with any percentage of 100LL and still be listed as "conforming G100UL."  So it IS actually a range of potential blends even if the original recipe is exact (which it likely isn't which is why each DHA is a blueprint for origination).

G100UL IS a specific blend.  But once it is pumped into a container with 100LL, it is not.  But neither is 100LL after it is mixed with some portion of G100UL.  You could say the same thing with 100LL and 115/145 (made once a year for formerly Reno, now Roswell air races).

You can get the exact recipe.  Just sign up with GAMI as a blender and sign their NDA.

[Pinecone]

3 hours ago, EricJ said:

Our local self-serve fuel vendor is very diligent about testing a fuel delivery to the spec before it goes in their tank.   I've been there when they've been processing a delivery.   It's impressive.   The guy delivering the tank was totally on top of it, too.   They're all involved in verifying the spec is met all the way through the supply chain.   It's one of the reasons consensus standards involve stakeholders from all parts of the chain, which helps make deployments successful and avoid surprises.

They actually run a sample through a GC-MS?  How do they "test" it?

[EricJ]

Just now, Pinecone said:

They actually run a sample through a GC-MS?  How do they "test" it?

I don't know the full span of field tests that they do, but they're doing acceptance testing for delivery, not a full chemical evaluation.    This is one of the things that generally happens in standard development, e.g., developing test strategies for field compliance verification, so that it is known that the fuels can be adequately acceptance tested in the field with practical equipment sufficiently to be able to reliably reject non-compliant or contaminated deliveries.   I observed them doing some color tests as well as specific gravity, particulate contaminant, and a few other tests that I don't know exactly what they were, but they had a checklist to go through before they accepted delivery and it was fairly thorough.   The delivery driver was right on top of it, like he knew he needed to support the testing for any delivery so it was a totally routine thing for them.

When I worked in standards the development of compliance verification tests was always a big part of the effort, as well as how to mark compliance verification.   Verification marking can't be done on fuel, so field testing has to be available as part of the verification system.

[Fly Boomer]

27 minutes ago, Pinecone said:

They actually run a sample through a GC-MS?  How do they "test" it?

I had a similar thought.  I can't imagine anybody at an FBO having sophisticated equipment -- never mind knowing how to use it.

[Marc_B]

1 hour ago, Pinecone said:

But neither is 100LL after it is mixed with some portion of G100UL

Just to be clear. G100UL comingled with 100LL is still “conforming G100UL.”  100LL mixed with any amount of G100UL is no longer 100LL. 

[Pinecone]

15 hours ago, Marc_B said:

Just to be clear. G100UL comingled with 100LL is still “conforming G100UL.”  100LL mixed with any amount of G100UL is no longer 100LL. 

True, but it no longer would meet an ASTM spec for it, unless the spec was wide enough to encompass 99.9% 100LL mixed with 0.1% of G100UL, which would make the standard useless.