I searched to see if anyone else was running 100LL avgas in their motors, and all I came up with was a brief mention of it in the fuel 101 post. "Premium" gas in Alaska is 90 octane... I was having a nightmare of a time tuning my motor with 90, it seemed to always be detonating, and it would "diesel" when I shut it off. I tried using bigger jets, then it seemed like I went from a super hot lean running motor to fowled up black sooty plugs with nothing good in the middle. I mixed 50/50 avgas and 90 octane and the detonating went away, my motor isnt running nearly as hot anymore (I finally got that nice paper bag color spark plugs), and the motor does not "diesel" anymore when I shut it off.

Anyone else run avgas, or have the same problems? It would be nice to solve my issues without having to buy gas at the airport.

I run 50/50 avgas/93octane. If I use a little fuel , like a gallon or two, I top off with 93 and add oct booster. My avgas here is 6.50gal...

Av gas is a great alternative to running race gas, here in Wi it's only about $1.50 more then premium pump gas depending on where you buy it. vp race fuel $12-14. I ran the av gas in my turboed mountain sled and it works great.

Its 5.80/gal here.. and 90 octane is 4.80/gal.... good thing my motor doesnt burn up a whole bunch of fuel... maybe 4 gal each time I go out. I wonder if the lead content in the fuel will gum anything up.

Decarbonizing the motor?

Where in lafayette can i find that avafuel i been using vp c12

I run premium and add 108 octane fuel.additive....only problem is it sputters and kicks a little when I turn it off.

Where you get your additive, Jefe?

And avgas = aviation gas. My local airport that is 2 miles away sells it 24/7!

Big bottle at auto zone for about 9 bucks.

Even Wal-Mart has 104 Octane Boost

I been buying stuff, but it didn't say what octane boost it was I didn't think.



I was running the river yesterday with a FULL load and I noticed it started the pinging once it got good and warmed up(15 min @3800) Guess I'll be running straight avgas from now on...

I got tanks full of aviation full out here in the plant and can't even use the shit, nor gas, nor diesel, i mean we make the shit and i have to pay for it, crazy how that works

Jw.. What exactly is the point in running this fuel? Av fuel of just booster. I always thought that it really didint do much without having timing adjusted just for that fuel?

I could be very wrong, but my understanding is that detonation can be caused by several issues: timing too far advanced, "lean" fuel burn, "lugging" the engine, poor quality fuel, overheating, poor quality oil,. If the timing is too far advanced, if a blocked fuel passage or partially blocked passage in the carb, running an incorrect size prop so the engine doesn't turn the upper limits of the rpm range,fuel that doesn't have proper octane, marginal water cooling, oil with poor lubricating properties. All of these individually or in combination with each other may cause detonation, pre-ignition and eventually severe internal damage.

The higher compression engines need higher octane level fuels. If you're runnin a stock motor, or have compression of ~150-180, you should be fine with supreme pump gas.

My motor guy just suggested I use a cooler plug. I'll keep y'all posted.

No matter what mods you have, the stock Champion plugs should be good.

I've had good luck with the autolite 3923's. They are a slightly cooler plug.

Thanks man! I'll check em out!

I've always thought of octane boosters as penis enlargement pills... they both cost alot and neither one of them actually does anything.

People think higher octane fuel = more power......

I have a 36 pro-drive bout 4 years old. Normally runs great but it looses power just like a fuel vent closed when i'm running with a load and wide open for about ten minutes or more. it's been doing this forever. Couple year's back i switch't from 87 octane too 92 octane that seemed to help. Now the problen is returning. Do i need to mix 92 oct and 100 oct?

sounds like you need a fuel pump.