3.7 V6 QC 3:55 - Stock tires were 245/70/16 and I upgraded to 265/70/16Dueler AT Revos. Mileage has dropped from 16mpg around town to 13mpg around the same time I got the new rubber. I don't really notice any difference when driving, once a slug always a slug.[:@] The new tires do make the truck ride better. Anyway, you think 3mpg loss could be caused just from the new tires / size change?

 

Yep larger tires take more power (hence more fuel) to turn them.

 

Really no difference when I go from 15mpg to 11 when I had my trailer hooked up. Hell a friend found out the hard way when his Ram went from 13 to 7 when he put 38" tires on it. Warned him, he didnt listen and then he whined about how much it costs to fill the truck up. Well a 5.9l with 38" tires will do that.

 

someone has a leadfoot.... just my thought...

 

When I went up to my BFG All Terrains, I lost about 1.5-2mpg

 

I've lost 2mpg when I went to the 265/70/16s...

So don't worry yourself a whole lot.

 

Something else to keep in mind is that since you went with a different rolling diameter, you really have no way on knowing what your mileage is. Your odometer will be inaccurate. If you have a computer telling you, it will be inaccurate. Also, your speedometer is now inaccurate.