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I successfully used auto fuel for over 15 years in my Ercoupe, until I let it sit for several months. The Continental C-65/75/85 are all certified on 73 octane aviation gasoline. See Spec 718 & 787. So when later engines were developed and more power was desired the fuel industry developed 100 octane fuels for anti knock properties. Continental the addopted the standard 80 octane fuel. When 80 octane became scarce and then finally no longer available at most locations, they specified 100 octane Low Lead. I understand that 100 Low lead still has about 8 times the lead of 80 octane aviation gasoline. That may not be correct. Running these small engines on 100 LL still can cause lead deposit problems, resulting in stuck valves, etc., especially if one babies the engine....as the combustion temperatures are not high enough to fully vaporize the lead... As I mentione above, I ran auto fuel for many years with no problems. Then I let the coupe sit for several months. I also topped the tanks with auto fuel that had a strange smell (AMOCO 93 octane) smelling of desile/turbine fuel smell...maybe some asphalt smell. I thought no problem. Then after sitting and no refueling, I developed a green sludge growth in the wing tanks, and header tanks. ????? Well, I wonder if this this IS the same algae problem seen with jet fuel, and the reason for adding a algacide to jet/turbine fuel ???? I sent samples to Amoco....they refused to comment. I think this was the result of contamination of the auto fuel with fuel oil ( the asphalt smell), and letting the Coupe sit for a long period without the replensihing of clean fuel..... Even tho I drained the sumps regularly, ( I got green water) , I could not completely destroy the algae. I even added prist ( like the turbine boys) , and this helped, but didn't completely eliminate the problem. When my tanks were cleaned and rebuilt it was difficult to remove all of the algae growth in the tanks......!!! I think the problem is that unleaded gasoline does not kill algae, while leaded gasoline does; due to the toxicity of the lead. I got a slug of contaminated gasoline ( with jet fuel or fuel oil, suseptable to algae growth), and it grew on the water condensation that occurs in the fuel tanks of all airplanes. That's why we drain the sumps.... (foolishly due to my Scotch Irish heritage, I didn't want to waste the contaminated gasoline. So I drained the tanks,and put it in two autos. Almost immediately both vehicles lost their gas guage operation. I refueled one vehicle quickly, and the gas guage again worked, the other car which is driven less often sat for several weeks., the gas guage still doesn't work. ....algae eats copper!) co-incidence ? So, after cleaning the tanks, I decided to again use avialtion 100 LL, or a MIXTURE OF AUTO + 100ll - even with the potential of lead deposits on the valve stems in the low powered engines.....I think its the best solution we presently have. Algae can be a problem, and is difficult to eliminate once aquired. I just wanted to pass this along.......no recomendation to either fuel.. mAYBE THE NEW AVIATION FUELS WILL SOLVE THE PROBLEM FOR ALL OF US. Harry Francis Blacksburg, VA. ========================================================================== ==== To leave this forum go to: http://ercoupers.com/lists.htm
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