This will probably sound like a stupid poto most, but I was wondering what kind of mileage you guys were getting with bigger than stock wheels and tires. I have 37" tires and have adjusted my oem speedo with my Triple Dog, and running 70mph I run about 1650rpm's. Should I get better highway mpg's because of the major drop in rpm's, or does the extra weight drag it down?

I know city driving will suffer, but in my mind cruising at about 70, I should get great mileage, even with the added weight.

Anyway, if you guys could let me know what you get or explain the mechanics of why I shouldn't get great highway mpg I would appreciate it.

 

Highway mileage at 75 with 35's = 17-18@2300+RPM
Highway mileage at 75 with 40's = 22-24@1800+RPM

Hand calculated multiple times. As soon as my truck gets over 2000 RPMs, it seems to suck the fuel down.

I drive my truck hard all the time everywhere I go.

 

Wider and taller tires cause more friction due to more surface area, thats why we get bigger and taller tires.

The other side is it also increases the frontal area of the vehical, by putting more spinning tire into the direct path of the wind it will cause more power to be needed to hold the same speed. At 60 mph you might get better, but at 70 you might get worse. It really depends on where your wall is, once you cross that speed it takes more power to hold each mph you go past it, and it ramps up very fast.

 

I think the OP has his Triple Dog calibrated incorrectly.

 

I don't know if it is calibrated wrong or not but I have checked the speedo with my gps and two stock trucks and it is right on, both at low and high speeds.
I don't know, I am not complaining about my mileage, I didn't expect great mileage when I lifted the truck but I was just wondering what others were getting with their tires.