Quote:
Originally Posted by ken0042
I find that the occasional tank of premium makes the car seem to run a little better, and I can measure the difference in gas mileage. Sure the gas milage advantage doesn't pay all of the extra cost for premium, but some of it.
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Then you may have an issue with your car which is actually making use of the higher octane. If your car requires 87, but you put in 91 and you improve performance and mileage, then there may be cause for concern because this shouldn't happen.
Other than that, it's a placebo effect or coincidence. 91 doesn't have more potential energy in it than 87 does.