[jrlnc]

Ok guys, I'm appealing to those folks here with the technical knowledge . . .

I have the '07 Fit Sport. I recently replaced my tires (those crappy Dunlops) with some really nice Michelins (Primacy MXV4s) from Costco.

The new tires are: 195/60HR15 88H

The problem is, when I bought the tires they did not have an exact size match for the old tires. I agreed to get the "taller" tires and am pretty happy with them. I run mine at 38 psi and the others were definitely firm (i.e. harsh) riding and very noisy. The new ones at the higher pressure are dead quiet in comparison and ride very smoothly and comfortably.

Problem is, I noticed a mileage drop on the first 2 tanks on the new tires and thought it was an aberration because of higher %age city driving and constant a/c use.

One day I was using my GPS and noticed that it was reading a higher speed than my speedometer. Very consistently when the speedometer is locked at 70 mph the GPS reads 73 mph. That jibes with what I've been finding because I seem to be passing everyone now whereas before I being passed more.

I know that if your speedometer is reading low, then the tripmeter and odometer are also reading low. (btw - The Honda dealer said they definitely don't recalibrate speedometers for tires.)

In calculating MPG, I have now been multiplying miles traveled on the tripmeter by 73/70 and then dividing by gallons put in at the pump.

MPG = Miles traveled (tripmeter) / Gallons at pump X (73/70)

Does this seem correct? Does anyone know of a different way to adjust the MPG number?