Octane rating of UL94 avgas

[Altydoc]

Swift fuels offers offers unleaded avgas, their UL94, which I read is basically 100LL without TEL added.
https://swiftfuels.com/fuel/unleaded-ul94-avgas/

I know that pump gas octane rating is an "average" of RON and MON, or R+M/2, and avgas octane rating is comparable to MON. That being said, what the octane rating of UL94 be in relation to pump gas? I've read that it would be approx. 96-98 octane R+M/2
I know that avgas is illegal for road use, and it has slightly fewer BTUs per unit volume than pump gas, so runs leaner, but I'm interested in using it for off road applications where an ethanol free fuel with an octane rating greater than 93 would be needed.
Thanks.

 

[Cujet]

As you probably know, the lower of the two aviation octane ratings is generally equiv to the MON (motor octane number) and for our discussion today, can be considered the same.

Motor octane number, is always (for our discussion) the lower of the two numbers we commonly use in the USA to compute the AKI. (motor octane and research octane) .

Motor octane number is determined under more stressful conditions.

So, with that in mind, if you want to compare a fuel with a published MON but unpublished RON to the AKI (anti knock index) you can only make a guess, but it would be correct to guess that the AKI would be higher than 94 in this case.

Interestingly, 100LL is said to have a MON of 100 (99.5 minimum) , an RON of 103.2 and an AKI of 101.5.

So, with the fact that Swift UL94 is the same as 100LL without the lead, it would be safe to guess that the RON is only slightly higher, and the AKI is also only slightly higher.


NOTE: 100LL is commonly tried and used as race fuel. It's not the ideal race car fuel and will not provide anywhere near the detonation resistance of properly chosen race fuel in turbocharged engines. Our testing in 2+ liter 4 cylinder turbo engines highlighted the limits of 100LL at anything over about 15 pounds boost in race configurations. In other words, it works in anything but high boost race applications.

NOTE 2: Fuels with MON and RON numbers closely matched are said to be quite stable.




SOOOOOOOOO, my best guess: Swift UL94 has an AKI R+M/2 of 96 octane.

I got there by adding the same 2 point spread that exists on it's sister fuel, 100LL.

 

[Linctex]

Originally Posted by Altydoc
I'm interested in using it for off road applications where an ethanol free fuel with an octane rating greater than 93 would be needed.


I think you are pretty safe with it meeting what you are looking to get from it.