Tell that to your local legislators who thought it necessary to mandate that you waste fuel in order to minimize safety and maximize revenue to the local governments and maximize carnage on our highways. In other words, you are looking at this wrong. I'd gladly upshift and drive safely at the most fuel-efficient speed of my engine in overdrive gear, if it was legal for me to do so. Often, I do so anyway. :) But at 78MPH, I am risking my license by driving in a very safe, sane, logical and fuel-efficient manner in over-drive.
Yes, I could do 55MPH in 4th gear everywhere. I would get decent fuel economy that way. But I'd have to put up with the extra engine noise generated at 3500RPM, while it's taking forever and a day to get anywhere. Plus, it's harder to hold a constant speed in 4th gear. Because I'm lazy, I generally shift up to overdrive even at relatively low speeds like 55MPH. But then, I pay for my laziness at the gas pump. The only time I get really good gas mileage is when I'm in a hurry and not as worried about getting hbuttled by the cops. IF I can maintain an average speed close to 78MPH for long enough, my MPGs go way up. But again, that's not exactly legal in most areas of the U.S. -Dave
