Quote:
Originally Posted by nickritter1992
if someone has experience with the change in diameter in tire vs FE please chime in
also was at the pump the other day and noticed 87 oct has 10% ethanol in it and the 91 said it was E free so gonna make that switch after the Intake results
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The 185/65-14 tires are 2.2% larger than the 175/65-14 tires. Your odometer will read lower with the smaller tires, so you need to multiply your miles travelled by 2.2% when calculating mileage. So your 33mpg from your last tank is actually 33.7mpg.
As far as going to 91 octane for 0% ethanol, it won't be worth the extra cost. E10 fuel has 2.5% less energy than E0 fuel, so in theory you'll get 2.5% better mileage with 91 E0 fuel, but lower octane fuels burn faster, so this will offset some of this improvement. I also bet you're paying more than an extra 2.5% for the 91.