Hey guys, I'm getting ready to replace the tires on my 04 h2 I purchased last year. Currently it has 35x12.50x16 toyo open country mt, the tire itself has done great but the wheel size is just to small for the truck. So if I change to a 37×12.50x17 or 37x12.50x 18 is that 2" going to decrease my fuel consumption noticeably? Right now the on board computer says I'm getting about 11.8 avg mpg. What could I expect from a larger diameter tire?

 

A larger tire has more rotational mass, so in general, your mileage will decrease. That's the general answer.
The best option is to regear, honestly if you really want to help improve your mileage a little & not accelerate like you're towing 15k lbs. You have 4.10 gears now. 4.56 gears would cut out all of the sluggishness when accelerating from stop. Your top end mg might be hurt a little, but not much.

The answer really is determined by the type of driving you do. If it's mostly city, regear, regear, regear. If that's the case, even consider 4.88s. If it's 50/50 city/highway, probably 4.56s are a good choice. Mostly highway, you probably shouldn't consider 37s, but something in the ballpark of 34.5 to 35 that's more of a highway tire and lighter.