Premium Gas

[churp]

I'm just an old toad but.......Higher compression does make more power thus better gas milage. Without computers on our engines 9:1 compression is about tops for 87 octane, the ECU is the only thing keeping the engine from self distruction at 10.5:1 by adjusting the timing because of the detonation sensor feedback. With better octane the timing can be advanced to a much more efficient state thus getting better millage and power.

An example is back in the early seventies gas crisis...one group modified a Pinto to try to improve milage. Through the use of another cam, increasing compression from 9:1 to 12:1, and using water injection to reduce detonation (research water/alcohol injection in combination with turbo/super charging) they increased horsepower 50% and milage went from 30 to 45 on a controlled track. Now 12:1 is pretty extreme but as long as you can control detonation (water injection) you can set your timing to take advantage of this. No ECU's back then, now we do! Now we have the ECU setting our timing through detonation sensors to the optimum setting for efficiency (we maybe could run 87 octane at 10:1 compression but without the real world timing adjustments done by an ECU, performance would be crap).

In other words due to the ECU adjusting timing in real time, YES you should get better gas milage and performance with higher octane fuel !!!!! Does it pay to use premium? If you get 3% gain in milage and premium is 2% more cost than 87 octane go for it because performance increases also. I don't have a scangauge yet, but I'd go by the facts before the myth that higher octane doesn't help. Computers have really changed the word since the 70's.

[static808]

Originally Posted by churp

If you get 3% gain in milage and premium is 2% more cost than 87 octane go for it because performance increases also.

this is where the problem lies for many of us: premium gas is usually 7-10% more expensive than regular. and i dont think we'll see a 7-10% in performance or mpg, so from a strictly economical standpoint, its not worth it.

--B