I have a 04 chevy silverado 6.0 with stock 16" tires & 410 gears I was thinking of going with a set of 20,s or 21" rims with a mid range tire on it. the problemI havewith fuel mileage is that i,am pulling 2100 to 2200 rpms at 65 mph at 60 it is 2000rpm,s at 55 it 1800 to1900 rpms truck gets 12.5 miles to the gallon I figure that if I can get the rpms down 150 to 200 rpms across the boardI should save enough tofuel tooffsetthe bigger tiresI drive a average of 40 thousand miles year.any ideals would be helpfull thanks.

 

you need to get a tire on it that is about 32-33 in. tall and that would almost be like running 3:73 gears instead of 4:10's which would bring you rpm down some. At 65mph I am running about 1500-1700rpm with 285/75-16 and 3:73 gears which are 33's

 

33.5" tall tires (35s), 4.10 gear, 70 mph, ~2100 rpm
with mods listed below I'm getting around 17 mpg hi-way at sea level, with 87 octane. However, I get 11-14 mpg city

 

i re-checked last night and it is actually at 1700rpm at 65mph

 

Which engine do you have? and do you still have the stock 16" rims? not sure what size they are on a 06 model.

 

Bump

 

5.3L. 18" aftermarket. Don't know the offset off the top of my head.