I thought that AViation gas had parafin in it, which contributed to extensive carbon build up within the combustion chamber/top of the cylinder heads.
I hate to ruin the illusion, but your car did not run any better because of the higher octane...it ran smoother because of A-The purity of the gas, B-The lack of ethanol.
The octane rating of a fuel only indicates its resistance to detonation. If your car is timed and jetted to run on 87, and all you do is pour 100 in the tank, there will be zero difference in performance. If you go further, to 105 and better, you'll actually see a decrease in performance and mileage because the fuel will be too slow burning for the lower octane settings.
Exactly. It gets in people's heads that higher octane fuel is going to produce more power when in reality it doesn't. It only resists detonation better in high comp engines and actually burns slower. If you don't have the compression to need it, race fuel is practically useless.
If you guys would, please explain why some of us have experienced a noticable difference when adding av gas to a souped up engine. (I did not time/jet my previous 360-was told premium {93octane} use only, 10to1 compression)- 'In our heads, the engine ran better/stronger.'- I wouldn't think that could be imaginary for multiple people. I do not think the people mentioning a noticable change are talking about 87 octane-stock motors.?.
I drive a few cheapo cars with my Mopars, but am not confused with the performance of one vehicle from another.
BTW, would it be prudent/benificial to re-time the motor if you changed your regular fuel usage significantly (from pump gas to av) gas ? Does this
resistance to detonation help if the mix is leaned out?
I thought ethanol added
resistance to detonation/octane, like E85 {15% 87 octane, 85% ethanol} has a 110?? octane rating. Why would an apparent change in motor performance be noticable then? Do you mean pure as in less inpurities?
In one experience for me with the change to up-to-10%-addional-ethanol fuel at the pump I drove a low compression, stock, two barrel 360 in a 5600 pound, four speed, 1977 D300. My buddies and I would tow vehicles from time to time. My friend asked me why I was refueling with premium during a tow and I told him that I experienced detonation during towing (car/trailor++weight) and he was adamant that it was not necessary. We then refueled with 87+ethanol only to experience significant detonation.
This motor was designed with low compression for use during the 70's 87octane bad gas era-I am sure timing needed to be changed but this experience seems to point towards someone being able to notice a change in octane usage.
I don't think that you are necessarily wrong-I just do not understand why some people's experience contradicts your quoted book/engineering like facts.
