Simple. Well, it WAS simple before gas was twenty bucks a gallon. :)
I'd tell them to try it themselves. Take a trip of mostly uncongested highway miles greater than 200. Try to keep your speed at 55 (tough I know, but try). Measure your mileage, preferably round trip.
THAT'S IT FOLKS, WE'RE OUT OF OIL 2368Ronald Evans I guess you've got your oil futures all bought up then.. You have data, but your logic is wrong. Circular reasoning. In order to know when the midpoint...
Then later, repeat the same trip at 70 or higher. If you're a good driver, let the car pick its own speed (just watch out for the cops, obviously). Most cars when nicely warmed up seem to settle into a comfortable cruising speed somewhere around 70 or so. If you can 'feel' where this comfortable cruising speed is, that's probably close to the engine's sweet spot. Measure your mileage again.
Be prepared to be surprised, as most of you will probably get significantly better gas mileage at higher average speeds (within reason, obviously . . . don't expect 120 to be better than 60, as 120 would put your engine too far out of its maximum efficiency range, also)
If people would just do this (and buttuming they knew how to calculate gas mileage correctly), there would be no explanation necessary. BUT, for those who want it, I'd again refer them to the brochure used to sell their car. Once they've seen the actual fuel savings at slightly higher speeds, the graphs and data on engine horsepower-torque-RPM will make more sense. Because they will probably have a good idea where the "sweet spot" of their engine is already, and (not coincidentally) the graph-data will likely show that the engine is producing a good amount of horsepower and-or torque at that point. -Dave
