i kinda disagree here with a few things. efxr8 11-13k? unlikely. good condition, low k's, manual ef xr6's fetch bout 14-16, good cond xr8 ef would b more 17's. the el xr8 bout 18-19k last time i checkd.
in regards to fuel consumption, goto http://www.trueblueford.com
they got heaps of info. no fuel consum. for the xr6, xr8 EL's, but they are the same engine as the fairmont ghia (xr6 & 8 motor) with the followinf specs:
Engine/Gearbox/Bodystyle. City Cycle. Highway Cycle.
4.0 MP EFI auto Fairmont Ghia Sedan. 13.0 8.0
5.0 MP EFI auto Fairmont Ghia Sedan. 14.5 9.0
Malchior is technically right with the performance side of it. The 6's were quicker but a 8 that was run in could just put a nose in front on the quarter. there is always capa superchargers.......