I have a 2009 silverado with the 20 in rim package. I
use it in dirt roads quite a bit and im thinking about
putting on one size bigger tires on it to give me a
little softer ride. Im just wondering if it will affect my
fuel mileage and if so how much? Also what is a good
all terrain tire for a quiet ride and wont throw to many
stones. Any advice is appreciated.

 

Mpg will be affected changin size, but not by much. A 285/55/20 toyo at2(tad wider than stock) or a 275/60/20 (tad taller than stock) sounds perfect for you. But don't think it'll make for softer ride. But either one will probably rub without a levelin kit