Some have already posted about bringing back the 55mph speed limit, but obviously, that's not very practical nowadays with today's modern vehicles.
My proposal--though I admit that my only data point at the present time is the fuel efficiency of my own vehicle--is not to exceed 3000 RPM in any particular gear, including the topmost gear of a manual or automatic transmission equipped vehicle.
As far as freeway speeds were concerned in the topmost gear (4th gear of a 4 speed automatic overdrive transmission), I noted that 2500 RPM was just a bit under 65mph, while 3000 RPM was around 75mph but not quite 80mph. Transmissions with higher gears may have a greater top speed even when keeping at or below 3000 RPM, but for now, I'm setting aside the speed limit issues in favor of discussing fuel economy.
Obviously, there will be some occasions where it may be necessary to exceed 3000 RPM, such as driving up a grade, but for the most part, my proposal applies to most surface streets and freeways that are on reasonably level ground.
Hopefully, there will be some reasonable discussion about this proposal and not just knee-jerk flames.
