octane rating

zman1621 · Post by **zman1621** » 21 Feb 2005, 22:50

I think that I already know the answer to this question, but because I am a poor college student, I am always looking for shortcuts. Anyways, I drive a 97 850 GLT. In the manual it says that the lowest octane for this car is 87. Can I get away with filling up on 85 every once and awhile. I heard that low octane creates ping in these high performance engines. I also heard that I may be able to mix 87 (or 91) and 85 in one tank to reduce the cost. Any thoughts....thanks

Guest · Post by **Guest** » 22 Feb 2005, 08:43

I read about this somewhere, but you can get away with using lower grade fuel in some modern engines because the computers will modify the timing. It will reduce the maximum output of the engine and won't perform around it's peak numbers, but as far as hurting the engine I think it's minimal.

Da' Moose · Post by **Da' Moose** » 22 Feb 2005, 08:45

You are the one to answer that question. Give it a try and listen to the car, it will tell you if it is OK with the switch or not. If when you use the lower grade fuel the engine has a ping you will know that the motor is not happy with the lower grade fuel.

Most of the time 87 octane is just a blend of regular and premium fuels, if you were to do the blending in your tank with the mid grade and the regular you might be able to find a happy medium and save a few bucks. I would take a scientific look at it and keep a log of how much of what fuel used and the resulting performance. One tank of high and one of low or there about, just to see if you can find the happy cheap zone for you and your car.

While yes, the manufacture has designed the car to run on the higher octane fuel a LITTLE ping once in a while will not hurt the car, it will affect the performance though. As a poor collage student I would not think that you are out racing your GLT on a regular basis.

Good luck, Da