Use the lowest octane you can without knocking (or triggering knock sensor), otherwise you waste money. That might be 91, that might be 89, it might be 93. I would avoid ethanol in the summer, I experienced stalling and poor fuel economy when I used it in hot weather.
Octane rating requirements will go down when elevation increases, typical is around 1 point per 1000 feet of elevation. That is why if you go to high elevation areas, the highest octane available might be 89 or 91. Where I used to live in Wyoming at 7200 feet, we had 85/87/89 for the most part. This is because the air is thinner and the car effectively has a lower compression and will produce less power (about 3%/1000 feet) so at 7000 feet, the car has 21% less power (a 200 hp car would have about 160 hp at 7000 feet) .
I run 89 in my stock car without any trouble. I get 23/31 mpg and full performance. Try the three out and see if you feel a difference. Outside temperature/humidity and other factors can have an impact on what octane you need.
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Originally Posted by Dan Burger Anyone have any exp. running anything less than 91 oct. with a chip? I hear it's "highly not recommended" by Jim C. among others. Thanks Dan '95 CS |