I've run a few tanks through my car now with a fairly stable tune (I'm not changing values all over the fuel map like previously, lol), and it's been hovering pretty consistent around 15-16 mpg on my 67 Dart with a fair share of full throttle stabs since it's just too fun to not. It weighs a little over 3200 without me last time I had it weighed. I've since swapped over to fuel injection complete with a new fuel tank and added a fiberglass hood, but I don't think it would be enough weight to make a difference mpg-wise. I've got a standard 833 (no O/D) and 3.55 rear gears and drive 20 miles to work on a 55 mph highway doing just under 3k rpm. 70 puts me over 3k, maybe close to 3500. I'd like to see closer to 20 mpg, but then I also realize I doubled the power my car used to have and have the same if not better gas mileage, lol. O/D or different rear gears would probably bump me up a few mpg, but I'd rather keep the fun factor since I don't commute in it daily.