The 3.92 and big tires really put a hit on the mpg. It is the width of the tire more than the height. I never realized it till pushing my wifes around the shop, waaaay harder to push with the wide ones when the steering wheel is turned even a little bit, even straight pushing it was noticably harder. I have owned and driven several of them and trust me you do not want the 3.92 even for town driving, the performance difference is almost imperceptible. A 318 with a 44re and 3.55s is faster than the R/T I have now.