Dave C.
That link shows your Galant getting a max. of 141 HP at 5500 RPM. The torque peak (148 ft-lb) is at 3,000 RPM, but more fuel would still be drawn as you revved higher in top gear. You'd exceed optimum torque but you'd still be generating more total power and burning more gasoline. When people drive beyond a certain speed you can actually smell unburned fuel exiting the tailpipe.
You should post a uniform readout (trip computer?) of your fuel economy starting at 55 and going all the way up to 80. If it's not a smooth curve it should tell you something's fishy.
You can't make a car go faster in top gear without using more POWER, and it comes at a price. Something is probably wrong with your calculations or your fuel system. I think it's the calculations (or trip computer?) because that engine is just too big to get 42 MPG. A 1.8L Corolla or 1.7L Civic is lucky to reach that figure on a flat road.
BTW, I think the original poster's 3,000 RPM idea is unworkable. We just need to get Americans to conserve as a way of life instead of waiting for crises. I don't see it happening until the current Administration leaves office.
C.T.
