# G100UL Approved

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#### Dana

##### Super Moderator
Staff member
The FAA finally approved a fleetwide STC for GAMI's 100UL avgas. Now we'll see how long it takes to implement...

#### Bigshu

##### Well-Known Member
Supporting Member
The FAA finally approved a fleetwide STC for GAMI's 100UL avgas. Now we'll see how long it takes to implement...

#### Hot Wings

##### Grumpy Cynic
Supporting Member
I understand that you can blend up a 10,000 gallon batch right on the ramp with common ingredients. You will need a license to do so.
Might be kind of impractical unles you have a source of aromatic hydrocarbons?

"wherein R1, R2, R3 and R4 are hydrogen or a C1-C3 alkyl group, said one or more aromatic amines comprising from more than zero % (0%) to about two point seven percent (2.7%) by weight of said unleaded avgas fuel blend;

(d) about sixty percent (60%) to about forty percent (40%) by weight of one or more dialkylated and/or trialkylated benzenes effective to increase the detonation performance"

and some of this for the 2%:

It is no wonder this stuff is higher density.............

#### Tiger Tim

##### Well-Known Member
Does the higher physical density come with an associated increase in energy density?

#### Hot Wings

##### Grumpy Cynic
Supporting Member
Does the higher physical density come with an associated increase in energy density?
No. Looks like actually less:

Aromatics are pretty low energy configurations of HCs. The alkyl substitutions (Rs) help with the energy density but it doesn't appear to be that significant unless they in themselves are longer chain.

##### Well-Known Member
Supporting Member
Although the energy density of the additives is lower per unit mass than the base hydrocarbons, densities of solutions are not that simple (think of ethanol in water, for example). G100UL is about 5% denser, and has about 1.5% more energy per unit volume, so it’s volumetric energy density is a bit higher and it’s mass energy density is a bit lower. In general, if you’re running at a constant power and filling tanks with 100LL vs G100UL, you’ll have a bit more range; but if you’re flying partial tanks to a given MTOW you’ll have a bit less.

#### Vigilant1

##### Well-Known Member
Supporting Member
In general, if you’re running at a constant power and filling tanks with 100LL vs G100UL, you’ll have a bit more range; but if you’re flying partial tanks to a given MTOW you’ll have a bit less.
I had heard that this energy density issue was one thing causing the FAA to delay approval, on the grounds that any true "drop in replacement" must have substantially identical energy density to 100LL so that existing carburetors and fuel injection systems (volumetric metering) would work perfectly, and acft range etc from automated systems would read right. I'm guessing that they are calling this new fuel "close enough".

#### rv7charlie

##### Well-Known Member
Supporting Member
Well, there are STCs to use regular mogas in avgas airplanes, so...

#### wsimpso1

##### Super Moderator
Staff member
Guys, this thread was heading into politics, and we do not allow that on hba.com. Posts citing these political points, arguing the topic, all deleted. Let's not go there folks.

oops

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