Unleaded high octane Avgas is now a reality, despite my disbelief!

[Cujet]

General Aviation Modifications, Inc.

General Aviation Modifications, Inc

gami.com

GAMI now has an STC for their unleaded AVGAS, which meets all the octane requirements of 100LL, including the 99.5 MON minimum, along with a matching RVP of 7psi. It seems the G100UL contains the same components of normal aviation gasoline, in somewhat different proportions. Plus a unique octane booster, a nitrogen containing amine.

It seems the fuel, for various reasons, can't meet the D910 specs that 100LL is produced under. But that does not seem to matter. The FAA does not certify the fuel. The FAA certifies what the engine/airframe manufacturer requires for fuel. G100UL contains 20% xylene and that increases the boiling point (end point) about 8 DEG F beyond D910 specs. (That won't matter, and is not operationally a problem, as that spec was made in the 1930's and we know a lot more about fuels now) .

The fuel contains:

Isopentane
Aviation alkylate
Mixed xylenes
m-toluidine nitro-amine octane booster, GAMI found a benign amine that works well. It supposedly comes from a product used in the "ink" industry and is produced by a Bayer offshoot company. Maybe it's similar to PEA that is used in Chevron Techron and that helps keep combustion chambers clean, as after 170 hours, the combustion chambers of normal engines are loaded with carbon.

In any case, the use of unleaded will allow the use of Synthetic oils, and probably greatly extend TBO. Our Rotax powered, unleaded burning motorglider uses Mobil 1, 10W-40 MX4t oil and the engine is spotless inside. Zero troubles and no plug fouling.

I am excited to try this new Unleaded Avgas.

 

[ekrampitzjr]

Excellent news. 100LL, despite "LL" = "low lead", has ~4 times the lead content of the auto gasoline with the highest lead content ever sold to the public, which was Sunoco 260 back in the muscle car days. Avgas has been the largest remaining source of lead in the environment. Even old hidebound NASCAR stopped using leaded fuel several years ago.

I hope this works out and the new fuel becomes the standard. Light aircraft were already becoming a target over environmental concerns, so maybe this will help.

 

[NitroM3]

The use of xylene is always interesting to me. I have been using it in gasoline fueled engines for decades both as mixed % and also 100%.
And I clean stuff with it as well. lol
The sad thing in California it is now regulated no sale item. So I have to drive over to RENO and pick up a couple of cases to keep on hand for my toys.

 

[MRC01]

The use of xylene is always interesting to me. I have been using it in gasoline fueled engines for decades both as mixed % and also 100%. ...

Same here. Back when CA state outlawed MTBE, gas stations switched to ethanol and the highest octane available at the pump dropped to 91. But the real situation was worse, because pump octane is (R+M)/2 but ethanol has low MON despite its high RON. So it can ping under load, causing the knock detector to engage, pull timing & lose power. I was active in SCCA at that time and my competition car lost about 10 RWHP on the dyno due to this change. So I started mixing 10% Xylene or Toluene with the pump gas, which restored the lost power.
So, I'm not surprised to hear this new 100UL fuel has Xylene in it.

Many aviation engines don't actually need 100 octane fuel. They run fine on 91 or even 87 octane so long as the fuel has no ethanol. They actually run better (cleaner, more efficient) with unleaded gas. But high performance piston aircraft engines do need the 100 octane. Even though they are outnumbered by the low power engines, they burn a lot more fuel. So if you look at it in terms of total gallons used, 100 octane dominates.

 

[y_p_w]

Same here. Back when CA state outlawed MTBE, gas stations switched to ethanol and the highest octane available at the pump dropped to 91. But the real situation was worse, because pump octane is (R+M)/2 but ethanol has low MON despite its high RON. So it can ping under load, causing the knock detector to engage, pull timing & lose power. I was active in SCCA at that time and my competition car lost about 10 RWHP on the dyno due to this change. So I started mixing 10% Xylene or Toluene with the pump gas, which restored the lost power.
So, I'm not surprised to hear this new 100UL fuel has Xylene in it.

Many aviation engines don't actually need 100 octane fuel. They run fine on 91 or even 87 octane so long as the fuel has no ethanol. They actually run better (cleaner, more efficient) with unleaded gas. But high performance piston aircraft engines do need the 100 octane. Even though they are outnumbered by the low power engines, they burn a lot more fuel. So if you look at it in terms of total gallons used, 100 octane dominates.

The switch to 91 happened when MTBE was still being used. That was more a matter of high demand for premium in California. Going to the lowest octane that met most car manufacturers' definition of "premium" meant that more was available.

 

[MRC01]

According to this article, they happened within a year of each other and are related. One reason was the gas companies knew MTBE was going away, but ethanol was still OK to use, but they couldn't blend in as much ethanol, so they reduced the octane. Of course there are always additional contributing factors like Unocal's patented 92 octane that other companies didn't want to pay to license.

 

[y_p_w]

According to this article, they happened within a year of each other and are related. One reason was the gas companies knew MTBE was going away, but ethanol was still OK to use, but they couldn't blend in as much ethanol, so they reduced the octane. Of course there are always additional contributing factors like Unocal's patented 92 octane that other companies didn't want to pay to license.

I had an Autoweek subscription and read that very article in the print edition two decades ago.

There was another article in Sport Compact Car magazine that said it was more about the demand and how fuel is refined and the output needs to be used up. Can't find the original, but some have reposted it to message boards. I think it was also in a Corvette forum. It barely mentions oxygenates.

BMW M3 Forum (E90 E92) - View Single Post - no premium gasoline in SoCal???

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www.m3post.com

You see, when crude oil is refined into gasoline, the refinery doesn't have all that much control over what comes out. Crude oil is full of all kinds of stuff, and a refinery simply separates it, sorting all the iso-this and hepta-that in order of density. The really heavy stuff, like tar, is near the bottom, while the really light stuff, like butane, is near the top.

Somewhere in the upper ranges of the stack are the components of gasoline. There are between 10 and 15 different blend stocks, each with a different octane rating, which are mixed together to make gasoline.

The crude oil being used and little else determine the amount of each blend stock available for mixing. Generally, if you just dump all the blend stocks into a bucket, you end up with something around 88 or 89 octane. If you're selective and only mix the good stuff, you can make 92, 93 or even 95 octane. But once you take out the good stuff, you're left with crap--something like 85 octane. Then you have to leave enough good stuff in the bucket to bring this pee-water up to at least 87 octane. This limits the amount of 95-octane gas you can make. If you make 93-octane premium instead, you use up less of the high-octane stocks, allowing you to make a higher proportion of premium fuel.

In the Midwest, where an extensive customer base of good old boys in pickup trucks consume vast quantities of 87 octane, demand for premium fuel is low enough to make genuine high-octane premium.

In California, however, Lexus-driving executives suck down premium fuel like it's Evian, so 92 was the rule.

 

[Cujet]

M-Toulidine, the Amine that is used to boost the octane comes from Germany. Just a quick glance at the price kind of shocked me. As much as $250 for half a liter. Yikes. No idea how much is required, but the patent shows up to 6%.

US8628594B1 - High octane unleaded aviation fuel - Google Patents

An unleaded aviation fuel blend. The fuel blend is provided by blending an unleaded aviation gasoline base fuel which may include iso-octane and iso-pentane, and an effective amount of a selected alkyl benzene to improve the functional engine performance to avoid harmful detonation sufficient to...

patents.google.com

 

[mk378]

There would almost have to be prior art on using this chemical as an octane booster. Every petrochemical under the sun has been studied for its potential to boost octane.

The real lucrative patent here is for someone to invent and patent a cheap process to make m-tolulidine, now that there is a market for it. Its price will come down as production increases.

 

[Cujet]

There would almost have to be prior art on using this chemical as an octane booster. Every petrochemical under the sun has been studied for its potential to boost octane.

The real lucrative patent here is for someone to invent and patent a cheap process to make m-tolulidine, now that there is a market for it. Its price will come down as production increases.

Amines are regularly used, think of Chevron Techron. But it's much like using paint stripper as octane booster. The common Amines have downsides. We are being told that m-tolulidine is substantially better and inert in composite (fiberglass or carbon fiber) fuel tanks, and/or fuel bladders.

As I mentioned in the thread title, it sure seems like it's being done, despite the failures of so many others. Up until now, I have been unaware of any functional, NON OXYGENATED unleaded fuel, at any cost, by any manufacturer that can achieve a 99.5 MON. Note: 100LL has a minimum MON rating specification of 99.5 (as per ASTM D910.

As you say, "Every petrochemical under the sun has been studied for its potential to boost octane" and the race fuel guys have been working on it nearly forever. The best unleaded, non oxygenated race fuel I can find falls many, many points short.

 

[GooseGestapo]

General Aviation Modifications, Inc.

General Aviation Modifications, Inc

gami.com

GAMI now has an STC for their unleaded AVGAS, which meets all the octane requirements of 100LL, including the 99.5 MON minimum, along with a matching RVP of 7psi. It seems the G100UL contains the same components of normal aviation gasoline, in somewhat different proportions. Plus a unique octane booster, a nitrogen containing amine.

It seems the fuel, for various reasons, can't meet the D910 specs that 100LL is produced under. But that does not seem to matter. The FAA does not certify the fuel. The FAA certifies what the engine/airframe manufacturer requires for fuel. G100UL contains 20% xylene and that increases the boiling point (end point) about 8 DEG F beyond D910 specs. (That won't matter, and is not operationally a problem, as that spec was made in the 1930's and we know a lot more about fuels now) .

The fuel contains:

Isopentane
Aviation alkylate
Mixed xylenes
m-toluidine nitro-amine octane booster, GAMI found a benign amine that works well. It supposedly comes from a product used in the "ink" industry and is produced by a Bayer offshoot company. Maybe it's similar to PEA that is used in Chevron Techron and that helps keep combustion chambers clean, as after 170 hours, the combustion chambers of normal engines are loaded with carbon.

In any case, the use of unleaded will allow the use of Synthetic oils, and probably greatly extend TBO. Our Rotax powered, unleaded burning motorglider uses Mobil 1, 10W-40 MX4t oil and the engine is spotless inside. Zero troubles and no plug fouling.

I am excited to try this new Unleaded Avgas.

Hmmm
$200 for the STC (iirc) and $7.00/gal at “select” locations don’t compute to me.
100LL Is still only $4.49/gal at my airport (this am).

 

[Cujet]

Hmmm
$200 for the STC (iirc) and $7.00/gal at “select” locations don’t compute to me.
100LL Is still only $4.49/gal at my airport (this am).

The price was projected to be around $5 per gal. Not cheap, that's for sure. However, the cheapest 100LL anywhere near me is now $4.35-$4.50 and my home airport self serve (F45) is $5.09.

I hope the current list price of G100UL is simply due to the low volume nature of the product. Maybe it will improve with time.