A lot has to do with driving style and conditions. I get around 25-26 on the pike, and could do better if it was not all up and down hills. However, in town, the traffic lights are poorly set and a lot of wasted time kills mileage. Probably the best all round gear is the factory 3.31. My regret is staying with the stock 2.73. It is only marginally better on highway travel, but is not the best choice in town.
2013 MCA Edition-Sterling Grey
Roush body kit - Splitters/hood scoop
Whiteline suspension w/Koni shocks