I hope this thread doesn't generate the old tired "If you want good mpg, get a Prius" or "hot rods and other fast rides aren't suppose to get good mpg". I have read a lot of posts here before posting this topic, and this forum has members that do understand that good performance, emissions, and mpg are not counter to each other. The folks that are running automatics with overdrive know this, deeper 1st gear, OD top gear. So, I'll start out with a description of the car and its normal MPG.

1.) 1923 Track-T, 1856 lbs, single 650 CFM on a dual plane, 0.64 OD manual trans, Jag IRS 3.54 to 31" tires. Engine sbc 383 stroker 10.27 to 1.
Steady state 70 mph highway cruise 25~30mpg
Stop and go city 16~21 mpg

2.) 2011 CTS-V, 4250 lbs EFI, supercharged and intercooled, 6 speed stick
Steady state 70 mph 23~25 mpg
City 14~18 mpg

3.) 2001 Ford 4X4 Diesel Excursion, 8000lbs, 7.3 L turbo diesel, 4 speed auto with 0.73 OD 70 mpg=2000 rpms
Steady state 70 mph 21~23
City 15~17 mpg

All who care to respond that have taken the time to calculate mpg, if you give enough info on your ride, I believe this thread could be rather informative. If you just don't give a hoot about mpg, just shine it on.