I didn't really notice any performance or mileage changes with the increased tire size. Probably didn't notice any since I only had 1100 miles on it when I changed tires. My mileage has gotten steadily better since I got my Ram up till around 5000 miles. I had a trip about 120 miles where I averaged 21.8 MPG. My Ram is a 4x4 Longhorn that weighs right at 6000 lbs so I'm not complaining about the mileage. City mileage is bad though, usually 14-15. I have 3.92 gears. No leveling kit, I have the 4-corner active air suspension which prevents me from putting any type of lift on it except for a 6" coil over suspension lift which would completely replace my air suspension that I absolutely love.