21 MPG whats wrong

[caineroad]

Originally Posted by tooter

You just implied another variable that no one seems to ever mention:

Wheel Diameter

Almost everyone here runs different diameter rims combined with a wide variety of different sized tires...

...and yet no one seems to be factoring in their wheel diameters to adjust their odometer readings to arrive at their actual gas mileage.

I changed my rims and tires just like everyone else, except I used a wheel diameter chart to determine the tire size and aspect ratio so as to keep the diameter within 1% of the stock diameter so that my odometer continues to give accurate readings.

Good job you brought this up... i didn't realize that.

Ever since I changed to 17' Cooper S rims, my speedo is slower than actual speed. Therefore the distance counter must be also slower (less), that would make sense to the loss mileage!