...Next, my 318 truck gets 13 mpg with 3:55 gears and 235 75 15 tires on an EFI motor being monitored by o2 sensors @ a very steady and smooth 70mph without OD. That mileage drops quickly when the speed exceeds 70. He has more cubic inches, more gear, shorter tires, and a big carb...
Sorry, can't help the OP with the tune issue, but I thought I'd toss in my mileage tracking since I regularly log this stuff and have done a good bit of tuning on my Carter TQ. This was a built 360 motor, 4K stall 727, 4.10 gears, 275/60-R15 tires.
Sooo...avg is 11.4 MPG (over 6 yrs and 6K miles), when I'm heavy on the pedal that's normally around high 9s and low 10s, but when cruising and covering a good distance I get as high as mid-13s.
Overall I'm happy with this, but I've done the tuning with O2 logging, good amount of TQ air bleed adjusting, pretty quick mech advance and absolutely running a vac can on the distributor.
YMMV
