Help, 2002 Denali, horrible gas mileage!

[Ramicus]

I have a 2002 Yukon Denali with 72,000 miles and I have a set of 22 inch wheels for it. With the normal wheels and tires the vehicle gets 12-16 mpg, with the 22's it gets 7-10. Why is this? I had them on a Tahoe and there was very little difference. Does it need a chip or what? Please help, thanks -

[maxwedge]

Are they the same diameter/ height as the stock wheels?

[Ramicus]

yes, they are very similar......

[east302]

Could be wrong here, but wouldn't the larger diameter tire throw off the odometer and therefore your miles/gallon calculation?

Post the original and new tire sizes if you can.

Or, the truck is working harder to turn the larger tires....but I doubt it'd make that much difference.

I think the truck's computer can be reflashed for the different tire size. Others here can probably offer more on that.

[maxwedge]

east302, correct on all counts.

[monogee]

When I purchased my 2005 Yukon Denali, the dealer told me if I planned on putting anything bigger than 21" rims on my truck, the transmission had to be brought in so they could recalibrate it. I never did put rims on it

[olddriver]

it is called rolling resistance. common on trucks with bigger/ wider tires. good lookin' but don't complain about mpg.