But if the ignition is retarded with 87 then it won't be the same. It will be lower.

I love how people start worrying about this as the price of fuel goes up. Yet the spread between 87 and 93 in absolute terms stays the same. In percentage terms, the spread is actually falling as the price rises. What that means is that the higher octane fuel has to increase mileage by a smaller and smaller amount to justify using it. This is exactly the opposite of the subjective feeling that most people have. When fuel is $1/gal they don't care about paying 20 cents more for higher octane. When fuel is $4/gal. they moan about the 20 cent difference.

As the price of fuel goes up and up, I'm more and more likely to stick with the higher octane fuel on a turbocharged car.

Stephen

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