Questions and Answers

Ford F-150 Proper RPMS? Q. I have a 1998 Ford F-150 4WD with the 4.6 liter V-8 and 5 speed transmission. I have been trying to keep the rpms low (between 1,500 and 2,000 ) while driving in order to get good gas mileage. To do this I am in fifth gear by 40 mph. I have 3.55 rear axle ratio.

Now I have been told by several guys at work and at a parts store that I am drastically reducing the life expectancy of my engine and clutch by running at such low rpms in such a high gear. Is there any truth to this? I know not to "lug" the engine and I am not hauling a load nor towing when I do this.

Steve

A. 1,500 to 2,000 rpm is a good range to keep the engine speed. Most professional truck drivers keep their engines in that range. Those big diesel locomotovies pulling those three and four mile long trains are only turning about 1,500 rpm.

I probably would't go into fifth gear below 45 mph, but if driving conditions permit it, 40 is okay. Low engine rpm in a car with an automatic transmission is bad because the transmission fluid doesn't circulate fast enough to keep the transmission cool.