I don't beleive the B12 (or the N12 for that matter) was designed for alot of highway usage. My B12 gets absolutely horrible mileage on the freeway. Oddly, my Turbo N12 at about 4000 rpms on the freeway actually gets toward 30 mpg. In town, I can burn a 1/4 tank driving around easily, but everything smooths out on the freeway (I have a heavy foot).