Calculating MPG with larger tires

LoL Yeah I found this yesterday while searching Google. It bugged me so badly I had to come back to it today and reply.

 

To those wondering:
Going from 265/70/16 to 265/75/16 is a 1.85% increase according to my speedometer discrepancy
Adjusting my odometer to this increase would mean that every 55 miles I add 1 mile to my odometer or 5000 miles I add 100 miles.

 

I just bought a $55 Ultragauge and let it do all the work of figuring mpg and adjusting for tire size. Has a nice speedometer on it and is calibrated for the tires. Done deal without spending hundreds of dollars on a calibrator.

 

I have the UltraGauge blue, how do you have it calibrate your tire size I have' seen anything on there to do so?

Im sceptical of the UltraGauge because I went from 23 mpg on 265/70/16 bald rugged trails, to 22-23 mpg on 265/75/16 cooper s/t Maxx
Ill take it, but Ive yet to fill,drive, fill, carry the 2 and calculate it since upgrading

 

In the menu go to calibration and clear it on miles driven, drive on a interstate using the mile markers for distance. After about 15 miles I'll stop next to a mile marker and adjust the miles to 15 driven. That sets the speedometer and calibrates for the size of the tires. Your mpg will be calibrated after a few fill ups when everything gets more data.

It should show you in the paperwork for the Ultragauge how to do it. I believe it's a download and doesn't come with the gauge though.