Originally Posted by Buzz38
I think too many people get caught up in the premium hype. The difference between lower and higher octane fuel is the burn rate. HIgher octane fuel burns slower to keep higher compression engines from detonating or pinging. That'* pretty much all there is to it. If your car doesn't specify that it needs premium you are wasting your money buying it. All my dealer recommends in our GXP is a good quality fuel. I always run Chevron 87. In 18k miles the car'* best tank of fuel is 17.1 mpg. My wife switched to premium thinking it would help improve the fuel economy until I saw the bill. No difference what so ever. On the other hand, if you feel better about life running it and can afford it, by all means fill er up.
To correct you Higher octane fuel does not burn slower than lower octane gasoline. The difference in Octane determines the fuels ignition temperature. For example at a certain temperature a piece of paper will spontaneously ignite. As everyone is aware the more you compress something the higher the temperature will be relative to the amount of compression. The octane rating is directly relative to the temperature that the fuel will spontaneously combust. (The higher the rating the better the resistance to that)
So, if you run a lot of boost or high compression in an engine and put 87 octane in your car the likelyhood that the fuel will ignite before the piston reaches TDC (Top dead Center) is higher if not absolute. We all know what happens if the fuel ignites before the piston reaches TDC lol... BOOM. Sight pre-ignition gives a knock but if the preignition is too severe, well, I hope you have sneakers on cause you'll be walking home.