Weight vs. Load Rating on mpg?

At some point i will get new tires... i loved the duratracs on my lifted xterra.
I can get them:
275/70 load e, 55 lbs
285/65 load d, 55 lbs
The 285s load e are 56 lbs...

I'd prefer the taller 275/70s (18)..

My guess is either will impact my mpgs similarly due to weight being same. Or if anything, 285s a tad worse due to wider and therefore more rolling resistance.

Sound right ??

or does the lower rating help somehow beside weight?

 

Id be impressed if you could find any repeatable difference from 1lb difference lol

 

Lol, I didnt take much of a hit when I went to 285/75/16 on my xterra, 4 inches more in diameter than stock.. but I keep seeing where people are taking hits so I wonder what????

But good point. My question really is relative to my stock Michelins. I assume same hit no matter... if any, whatever that may be

 

The issue isn't so much weight as rotational inertia. Diameter is a 4th order increase in moment of inertia, so a small increase in diameter requires substantially more energy to accelerate it. That coupled with increased rolling resistance like you said, is what will make you lose mpg.

I don't know what you get now, but I'd expect 14mpg if that's not what you get already

 

275 70 duratracs no drop in mpg hand calc.