I spoke to a fuel system engineer and the conversation inevitably came to the low quality of today's gas. He recommended putting 10 - 20 gallons of AV gas into the boats tank along with the normal 10% ethanol gasoline. His point was that the AV gas is much more stable than automotive gas, it doesn't contain ethanol and has a low lead content to protect the valves. He also recommended a dilution of AV gas in antiques cars.

It somewhat makes sense but I wonder if anyone has actually tried this. The 100 octane of the AV gas would be diluted and would slightly raise the octane level of the normal gas as another bonus. The downside is that it's quite expensive, somewhere to the tune of $6 per gallon. Could be worth it in small quantities if it had a beneficial result. I don't know.

I have used AvGas in old high compression cars, and some air cooled stuff. It's kind of a strange beast. The octane is rated differently than the methods we are used to at the pump, so its not quite 100 octane, and it has LOTS of lead in it. "100LL" is low lead compared to the old aviation gasoline that had tons and tons of lead in it.

We used to have to regularly clean the plugs on the airplane if the mixture was not leaned religiously during ground ops.

He is correct that it is a very stable fuel, and it is precisely controlled so quality is very consistent. Most of our motors wouldn't benefit much from it. I wouldn't even think about running it in an EFI motor without a proper tune.

It sure does smell good though

I run av gas in my jetboat, agree that avgas will help offset ethanol issues, but so will stabil

Im wondering the same thing,our marinia here has Cheveron 93 NON ethanol gasoline at 4.49 a gall, I can get Sunoco 110 leaded for 7.45 a gall.Last year I put 25gall of the 110 in with 93 oct and could tell a differance,even with that little bit in it,it idled better and you could smell it.

so if I mixed av gass and marinia 50/50 that would make it 5.25 a gall,
mix race gass and 93 non ethanol 50/50 would be 5.97 a gall.and that would be alot more lead in it

also will a air port sell ya more than 5 gall at a time?

Rob
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I've run AvGas in lots of high compression naturally aspirated street cars. If you decide to try it, make sure you add more fuel as it is lighter than actual race gas. There's been arguments over the consistentcy of AvGas due to the different altitudes and density altitudes it made to operate in but I never had a problem.

Ah the smell of AV Gas - that's a memory coming back. There was a cat on the lake that had trip blueprinted 2.5L merc's that would ONLY run AV in it.

I can't say if he had any less issues with longevity in his motors but I think it gave him a sense that he was doing more than hoping the marina pump gas would suffice....

I didn't think you could still buy it "retail".

I must have been misinformed.

Are you guys buying it right from an airport or by the drum?

Why bother with AV gas, just contact your local VP Racing dealer .... http://www.vpracingfuels.com/

It's a fairly common misconception that higher octane is better. The higher the octane the colder the combustion temperature. This is less efficient in engines that don't need it to help thwart off detonation. You want to run the lowest octane gasoline you can get away with without detonating.

AVGAS..... This was talked about a lot in the 2 stroke world. Think about what its designed to run. True it has higher octane to prevent detonation at sea level. though at altitude air is considerably "thinner" resulting in less compression. Its also much colder at altitude which is why avgas contains various anti-icing additives. While a plane engine may see a heavy load during takeoff, most of the time it is cruising along at a steady rpm under moderate load. both rpm and load being conservatively within the engines limit because the risk of gernading a motor at 20.000 feet is really not that acceptable. Avgas may have lead and other appealing charachteristics but it simply is not formulated or designed for use they way we use boat engines.