Originally posted by Ryde _Or_Die
I don't always agree. If you have an NA 4 cylinder that is stock and they tell you to run premium, theres no reason to unless it has an extreme compression ratio. It doesn't "burn cleaner," "give you better mileage," or any of the other myths. Octane rating is just as the article states; a determinant in when knocking will occur. Different brands of gasoline may contain detergents and other additives, but it has nothing to do with octane ratings.
ANNNIIIITTTT Wrong. The manufacturer tests each octane level for the car. And odds are if you have a low HP 4 banger... you have a 89 or 87 octane requirement.
I remember I had an Interpid and the 3.5 liters demanded 91 while the 3.0 liters were good with 89. My buddy that had one (3.0) got better gas milage and performance from the lower octane while mine pinged with anything less than 91.