ORIGINAL: earlwb
Many of the RC car specific glow fuels have a lot less oil in them. Sometimes as little as 8% oil in the fuel. So they get the extra power by having more methanol and nitromethane in the fuel as compared to model airplane glow fuel with 16% to 25% oil in it.
I think the RC car fuels evolved like that over time as the RC car people kept wanting more power and speed out of the engines. Plus RC car engines usually have a very short life anyway.
Anyway, it is why I always tell people to not use car fuel in a model airplane engine. When you think about it, a RC car engine doesn't go full throttle for every long, they usually run in the midrange throttle range a lot with short WOT bursts for the straightaway. So the engine tends to load up with extra oil at low throttle settings and blows it all out on the WOT burst, then repeats the cycle around the track. Someone a long time ago figured out how low they could go on the oil content in the fuel and still have the car engine work.
But with a airplane engine, most people tend to fly WOT or full throttle all the time. So then there isn't enough oil in the car fuel to support the engine properly.
I know for a lot of guys, car engines dont last long. The fast rpm they turn (some over 40,000rpm) tends to bellmouth the liner faster, among other things. Most of them are never broke in properly. Mine have been run on 20% nitro 12% oil for a number of years, though I recently dropped to 10% oil to see if there was much of a difference. Slightly more power, and still plenty of oil out the exhaust. Most premixed car fuel is 8-16% oil, with most of them being an 80/20 synthetic/castor blend. If you think about how long a car engine lasts running 35,000+rpm, gallonwise, compared to an aircraft engine running half that rpm.. I would think the amount of run time would be close to the same provided the break-in was indentically, and run on their respective fuels.
There was something written in a magazine earlier this year that in car engines, more than 8% oil is a waste as it does not promote longer engine life like one would expect. I am on the fence about that, as I've never worn out an engine to date. I have a 65mph 2wd 1/10th scale stadium truck with a 3-port .20ci engine that runs very well on 15%nitro/18%oil byrons airplane fuel (still breaking in), but it really runs fast on 20/10 fuel. More oil slows them down some, it seems.. but they run fine on more oil. Most guys want the instant cleanout and transition, of course at the expense of lubrication. I'm not a believer of synthetic oils being better in the car engines, only because they run hotter and in some cases, heavily loaded down.
So on the subject of oils.. Do Ester oils burn at that much of a a higher temp than Pag oils or are they about the same? Aren't Ester oils derived from natural non-synthetic base stock?