Originally Posted by RPM
My father-in-law HATES paying for premium fuel. He had a Park Avenue Ultra (SC 3.8) a couple of years ago that was supposed to take premium - but he used 87. This resulted in constant engine 'pinging,' decreased performance, and other issues.
The pinging comes from pre-ignition that can easily take place by using lower-than-necessary octane fuel. Higher compression motors require a higher octane fuel. The higher the octane, the more difficult the fuel is to ignite, and thusly will not ignite until it reaches the combustion chamber.
High-compression motor + low-octane fuel = pre-ignition = bad.
So if you hear pinging, use higher octane fuel.
Also, the octane rating is not going to have any effect on gas mileage.