Today's modern automobiles are much more efficient than they were back in the 1970s. They are more aerodynamic; the engines are more efficient; the power and torque curves have been engineered for modern highway speeds of 65-plus mph speeds.
I own a 2004 Ford Expedition that gets 17.4 to 17.6 miles per gallon on cruise control at 55, and 18.1 to 18.4 on cruise at 68. My 1996 Ford F150 got similar mileage. My Nissan Maxima got better mileage at 70 than at 55. My two sons and daughter own an Acura, GMC Envoy, Suzuki, Dodge Dakota, Ford Taurus and Ford F150. They all get better mileage at 65-plus than at 55.
I'd bet if most of the readers were to fill their tanks, drive to Columbia, S.C., at 55 on cruise, then fill up, document mileage and drive back to Augusta at 65-plus, fill up again and check the mileage, they would be pleasantly surprised. Most would get slightly better mileage coming back, and the rest would get at least equal mileage.
All reducing the speed limit will do is increase delivery times and costs, take people longer to get there and increase road rage, while not saving any gasoline. Want to save gas? Cool it with stomping on the gas. At stop signs and traffic lights, take a little longer to get up to speed, and back off a little sooner when coming up to them.
Jack W. Dalton