Even with gas prices cresting above $4 a gallon, large SUVs, pickup trucks and even Toyota Priuses barrel down freeways here in suburban Detroit at more than 75 miles per hour -- well beyond the 55 mph that was the national speed limit during the '70s and '80s.

If the U.S. Energy Department's calculations are right, all these lead foots could save the equivalent of 29 cents to 94 cents a gallon if they slowed down just to 60 mph -- and reduce the fuel they burn by about 7% to 23%. But most of my neighbors and I still choose...