Tires/Milage Advice

[Murf]

If I go from the stock 245's up to a 265 tire on my GMC DuraMax - how will that effect my fuel mileage and towing capability?

The 245's look so puney but I'm afraid of screwing up factory settings and loosing out in milage.

Any advice would be appreciated -

M.

[iljusin]

In city I lost almost 2m/gal (from 16m/gal to 14m/gal)

[Craig M]

A switch from 245-75R16 to 265-75R16 is about a 3.6% change. When reading 65.0 mph, actual speed will be 67.3 mph. Other have changed to 19.5" and 20" tires with increases greater than 3.6 % and are happy with their vehicles. The 16" diameter tires are puny, but the 265's do not add very much. 19.5's give good load capacity and looks!

[FJ40INTOW]

I did this upgrade but waited until I needed tires. I bought some H2 Hummer wheels on EBAY. They were 8.5" x 17" and I was able to get them for $204 for set of 4 plus $65 shipping. The 265's look real good and wear very even on thes wheels. The mpg went down a little on the DTC but the speedo reads closer to actual now so it may be wash. My DTC shows mpg average from day one at 19.1 and I have 87K miles on it.