The difference in fuel economy form rims tires is down to...
1 - weight of the wheels
2 - weight of the tires
3 - rolling resistance of the actual tires installed
4 - small bit down to sizes/widths exposed to the wind
Overall diameter of the two combos can effectively be identical, so that being equal, just having a larger rim won't affect MPG. Going with an actually taller overall wheel/tire package can affect it, however. And again, if the weight of the wheel increases, that hurts MPG. "Significant" is a very subjective term, too. Is 2 mpg significant in your mind? Or is it more like 5 mpg?
Having low tire pressures can drop a MPG or more.
Driving with your windows down can impact you to the same degree.
They do - in all of the various MPG thread here...and folks are posting on Fuelly as well - which, if you can find a few with the trim you seek listed, will give you a pretty accurate view of things.Ok..so how about some guys with the ED Crewcab 4x4 with 20" rims post up some of your MPG numbers please..