My Valiant averages about 14mpg overall, since I daily it, and unfortunately my commute is not exactly highway....yes , technically they're all 55 or 65 mph roads, but they're only like 4 minutes each. The most I have ever gotten was 21, if I drive on the interstate for the whole tank.
When I bought it, it had a BBD carb conversion, 205/75R14 tires, and was otherwise stock. Currently it has a motorcraft 2100 1.08, a 2" exhaust (the basic dutra type that reuses the old manifold for back half and merges into a single larger pipe), and 195/75R14 rears (apparently the store ordered the wrong ones but I didn't notice for a few weeks; oh well, that's closer to the size it came with, and the 4.5" wheels probably can't take the 205s too well anyway; I have yet to switch the rear axle to the large bolt pattern, and I'll get a less skinny wheel after that is done). Though, the "21 mpg" figure was when it still had the BBD and stock exhaust (can't remember when the tires changed), and I just haven't made a long enough trip since then.
A904 trans and 2.76 rear.
