Contour Enthusiasts Group Archives Forums Modifications Duratec Performance Racing Fuel ?

Originally posted by Justin T:

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Sports Compact Car magazine

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That explains a lot already. On a normal car with the stock correct calibration, running higher fuel will not give you anything. You have to increase the timing with higher octane fuel to see some possible gain. They probably have more gain on the boosted engine because on 93 octane gas the timing was retarded by quite a few degrees to prevent pre-ignition.

i know i have a zetec but when i started puttin 93 in before my chip came, here were my results: not better MPG (probably worse), gas costed more, engine didn't run quite as nice and didn't have the same "go" as it did with 87 octane. of course now the 93 octane is very helpful.

Well it shows what it should. Early on in the RPM cycle, you see greater gains in horse power and torque in 91 octane fuel. But as you get higher (it looks like above 5500 rpm) you get better torque and horse power from the 104 octane fuel. No big surprise. That's how NASCAR vehicles are able to run at such high levels of horse power. Unfortunately for those of us with vehcles limited to 6500 rpm and redlining at 7000 rpm, 104 octane fuel just doesn't offer an advantage.