I had a little time to test the MPG in a couple of gears at 38mph in 5th 45mpg, 4th 36mpg, 3rd 32mpg on a level road warmed up. Might be more interesting on a down slope in neutral where you maintain a constant speed in neutral coasting and just rev the engine at different RPM - since the net result is to have no change in speed then having it in neutral achieves this - this gives you a no load baseline for engine rpm to fuel economy at a speed that the ScanGauge can operate with.
Next would be in different gears going up a steep long hill to see if light reving or lugging gets better mpg results.
BTW I still see no change in MPG readings in neutral, 5th, 4th, or 3rd going down hill no throttle other than the MPG change due to speed change. I see a reduction in MPG if the engine is reving too high and that threshold rpm needs to be measured more exactly.
I've been warned by a number of people not to lug 5th gear to much, a mechanic friend of mine said was saying that at least on hondas, and I would suspect other light cars, that 5th gear isn't as heavy, because you would figure most people are going to use it for cruseing at higher speeds, that it's loads are more consistant, I've been paying more attention to my shift light, and noticing that on flat roads it will come on untill I'm in 4th gear going 35mph, engine spinning around 1,200rpm, can do 40mph in 5th, but at least for my car it seems a little slow for that high of gearing.
I'm in 5th approx 90% of the time, shifting from 2nd to 5th at 20 MPH when not hill climbing. At 1200 I'm only at 32MPH.
You sound like you drive a lot like I do in my Saturn. Your gearing also sounds similar. I'll check tonight and see how fast I'm going at 1200rpm in 5th. Once, when it was late at night and there was no traffic, I got into 5th and took my foot clear off the gas to see how fast I would go in 5th at idle. It was awhile ago but it seems like it was around 10-15. It didn't really shudder too much either. ;-)
Horsepower is how hard you hit the wall, torque is how much of the wall you take with you.