Does tire size affect mileage?

I recently changed the stock 17" wheels for 22"s with 345/45/22 and I added a k&n cold air intake kit at the same time. After I did this on my truck, I tried driving withouth flooring the truck too much and I noticed an big difference in mileage:uhoh: . I don't know exactly how many mpg does the truck because of the bigger tires/rims and difference in odometer readings, but the tank used to last me 1 week and now it lasts me 2 weeks:runaround: . Aren't bigger tires supposed to cripple mileage?
Thanks a lot for your feedback on this.
Cesar

Larger rims require more RPM around town, stop go stop go, requires a lot more gas to accelerate, thus horrible MPG. But if your doing lots of highway crusing, they require less RPM in 4th to turn the tires, thus bonus MPG.

Seeing those gains you must be doing mostly highway on cruise control?

I recently changed the stock 17" wheels for 22"s with 345/45/22 and I added a k&n cold air intake kit at the same time. After I did this on my truck, I tried driving withouth flooring the truck too much and I noticed an big difference in mileage:uhoh: . I don't know exactly how many mpg does the truck because of the bigger tires/rims and difference in odometer readings, but the tank used to last me 1 week and now it lasts me 2 weeks:runaround: . Aren't bigger tires supposed to cripple mileage?
Thanks a lot for your feedback on this.
Cesar
tires will effect gas mileage . there is a difference in rolling resistance. the tires you installed are low in rolling resistance when compared to stock wheels. in bad weather stock rubber gives better traction. trade -off...........

Not only rolling resistance; but rotational inertia.

It takes a lot more energy to get those 20's from rest to 25 or 40 mph and takes more energy by the brakes to slow them back down to zero.

Around the outside edge of the tire is the biggest place to gain or lose advantage when worrying about energy gain/loss. Ask anyone who rides a bicycle.

As knogoodidleft said; at highway speeds they want to keep rolling; so at speed you're okay; they just really suck in stop/go situations.

I know; I have BFG all terrains.. LOTS of rubber on those knobbies.

I changed from 255/70/16 General ATs to 265/75/16 BFG ATs and lost a lot of mileage. My old Generals were pretty bald though, and now my back end doesn't lose traction while driving down the highway in the rain. So like j cat said, it's a trade-off.