I am contemplating burning avgas straight in my 66 L-79, and am wondering if anyone has done it straight or do you mix with pump type gas. The avgas is low lead (2 grams/gallon) and 100+ octane. It's very competitively priced when bought directly from the airport pump, as it was only 30 cents higher than 89 octane unleaded about 3 weeks ago when I bought the first stuff. Any suggestions would be appreciated.

MY $.02 would be to mix it 50/50 or so if your engine is close to stock or all avgas if highly modified...

Keep us posted on the mileage difference between the two.I'm curious on the results of the two.

Caution: Avgas does not have the antiwear additives that automobile gas has. A friend of mine ran it in his BBC one race season and the top rings of all the pistons were nearly ate away. :(

I've heard that avgas isn't the best thing to run in a car as well. Avgas is meant to vaporize at lower pressures and low temperatures that are normally encountered while flying. A automobile engine doesn't see the same conditions.

Definately mix it, it burns very dry and hot it will prematurely wear everything that regular lead fuel comes in contact with. This is from experiance.

Ive also heard that you can add a little bit of oil too it too make it a little bit better for the motor. I dont know how much too add or if this is right but you might do some checking.

I have used avgas in my 383 for 2 years with no problems, it works better for me as I was having run on problems when turning off the ignition with regular pump gas. 100 low lead has some lead in it but not as much as the old premium that we used to burn in back in the 60's. Lead is a lubricant for the valves where as auto fuel doesn't have this property. Valve seats had to be induction hardened with the demise of leaded auto fuel so the valve seats wouldn't erode. I run 100% av gas, no mix with auto fuel. Avgas has a higher vapor pressure because it needs to be stable at high altitude. This won't hurt anything other than possible hard starting in the winter time, although we still get aircraft engines started at very low temps. There won't be any vapor lock problems in the summer. This works better for me as 90+ octane auto fuel is hard to find here in western Ks.

Even though the blue color avgas is called 100LL for low lead it has a hole lot more lead than leaded fuel ever had and is not designed for automotive engines.You would be better off running about 2 ounces per tank of Toulene.

http://www.osbornauto.com/racing/race2avgas.htm

DO NOT RUN AV GAS STRAIGHT!!!!
Will run very lean even mixed!!!!
Will cause engine temp to increase as well.
Brian

i have used it with no problems but remember it is Illegal to run on the street as it is not taxed as a motor fuel. Chances of getting caught are probably slim but fines could be ugly! Just something to think about.

Get high octane racing fuel instead. I mix 5 gallons of leaded UnoCal 110 octane and fill it with unleaded pump premium. Never a knock and I can run all the timing the engine can handle. There is enough lead in leaded racing fuel to keep any engine happy.

Avgas has too many limitations and your engine was not designed to run on such fuels. And then there is the legality and tax issue.

Or just add toulene to unleaded pump premium.

i posted this very question a month ago here and got similiar responses. Some people said OK...many said No way. It seems like there should be a correct answer. I am a private pilot so I have access to the Av gas at about 2.80 per gal but decided not to go that route. I'll tell you what i did:
I was having detonation problems that I couldn't get rid of with octane boost and if i retarded my timing I hated the performace. I decided I was going to try mixing the 110 with pump 93 just enough to get rid of the "ping". I put 5 gals of 110 in and toped the tank off with 93. I think it is a 18-19 gal tank so it is about 25%. WHAT A DIFFERENCE. I would have never expected that much from a mere 25%. I can't get the thing to "ping" now and it just responds to throttle. I paid 5.65/ gal and it was worth every pennie.

Thanks for all the input, I'm running 11:1 compression ratio, and only on the street, no strip time. After reading all the replies I think I'll go back to VP, 5 gals per tank full.

Information I got several years ago on 100LL (Low Lead) Avgas was that the lead content is 12 times higher than the old leaded gasoline for automobiles, and that Avgas has a very long shelf life. If you are burning it for lead content, you can mix it with pump gas at an appropriate ratio to get a good lead level.

A friend of mine stores his cars with mostly Avgas and never uses Stabil. He's never had a problem with deterioration of the fuel.

Woj

50/50 mix worked well for me for many years. No ill affects., DAVE