Once the initial break in was done and a few timing adjustments, the mileage has been consistently 15 to 17 around town and up to 23 on the highway through the last 8 months. I found that the 5.0 doesn't even use half as much throttle as when accelerating with the 2.3 and the gearing is set up to drive in 5th gear on the t-5 comfortably from 40(1300 rpm) to 70 mph(2000 rpm). When carrying a load of any kind from 200 to 400 lbs, the 2.3 was full throttle just to keep up with tractor trailers going up the pass while being passed. The mileage was dropping to around 14mpg, and around 19 to 20 with no load. It had been overhauled at 100k miles and didn't improve the performance any.
5.0 (306) from worn out gt mustang
Exploder 31 spline tracloc,linelockin 3:55 rear w/discs
S & R Customs in the works...