Would switching from the stock 245 highway tread to a 265 BFG all terrian tread hurt the highway mileage by about 5mpg at 65mph?

I used to get 22-24 at 65, now with the 265's it just seems like the engine is working harder than it needs to.......and I only get 16-18 at 65 and barely 20 at 60mph.

I know the bigger tire is more mass to spin but would the more aggressive tread pattern hurt mileage as well?

I have the BFG's in the same size, didn't keep the stockers on long enough to see a difference. I can see a small drop in mileage but that sounds like a lot. What pressure are you running them at ?

They are load D and I am running at 65 i think, whatever the max is. I ran the 245 at 75, max was 80 on those.

The diameter of new 245's is 30.5". Worn 245's will be about 29.5" depending on how far down you go. New 265's will be 31.6". The speedometer would have been reading about 4% faster than reality with the worn tires. The with the new tires about 4% slower than reaility. The total speedometer change going from worn 245's to new 265's would be just under 8%. The math says that your 23 average at 65 mph was probably closer to 22. The 17 average now is closer to 17.7. That's due to the tire size. So, that alone does not explain what's going on.

I think that the load range D tire will be squatting more under the same load than a range E tire. The more flex you put into the sidewall, the more it affects the mpg's. That may hit you for a couple mpg's.

I would jack up all 4 corners and inspect the brakes. You may have a dragging disc from a sticking caliper -- very common.


By the way, I went to a 255/85-16 which is 33.3" tall from a worn 245 and the mpg's are the same or a bit better. So, you shouldn't have been bit hard, but mine are "E" and stiff as a high school woodie.

jb

I noticed a drop in MPG's with my 265 BFG AT's and I believe it is because of the weight of the tire. I too am running D's, but have 55psi up front and 45-50 in the rear.