70 MPH Speed Limit Will Likely Reduce Fuel Efficiency, Researchers Say

Signs for the new 70 mph interstate speed limit in Wisconsin are going up this week, but some researchers say vehicle fuel efficiency will likely be going down as a result.

Consumer Reports says it does monthly tests of fuel economy on normal driving surfaces and not in controlled environments. Automotive specialist Mike Quincy said in one test of a four-cylinder Toyota Camry, there was about a five-mile drop per gallon when increasing speed from 65 to 75 mph.

“So, just because you have a green light to go a little faster, you’ll spend more for gasoline,” he said.

Quincy said if people keep it to 70 mph, the drop in fuel efficiency might be a bit less. He suggests removing extra weight from the vehicle and keeping tires properly inflated to partly offset the efficiency decline prompted by the new speed limit.