tire size vs mpg

[Guy Brooks]

I have a 71 3/4 ton 4x4 with a 292 and 410 or 411 gears.with the high price of gas I am thinking of gearing and motor options before I start the rebuild . I know a higher gear will inprove mpg .installing taller tires will make it higher geared but this will lower mpg or it did for me on other trucks.I have found nobody who can explan this to me .maybe someone on here knows thanks.