DrewE wrote:
I very much doubt the "economy" tune gets better mileage at equal power outputs and RPMs. The "premium" tune just lets the engine produce more power (and of course also consume more fuel) when pushed hard, and possibly alters the shift points to favor higher gears more.
You won't get 12 mpg with a typical class C motorhome at highway speeds with any gas engine, at least not without a rather radical redesign of the body to improve aerodynamics (which will necessarily also reduce interior space for a given length). It would be nice, I agree.
Drew that was RV hyperbole, to make a point. I don't know how to make those smiley faces that some on here make.