WHy would cold weather make for worse gas mileage? One of my SHO's gets abour 22 traveling @ 75-80, and I know it is running a bit rich. I expect 26+ after all tuning, and this is for a highly modified SHO. You should expect 28-30 for a well maintained, normally driven (keep your foot out, average highway speed of 70 or so) SHO. Even with your foot in it and lots of city driving, 22-24 should be the norm.