Consumer Reports wanted to find out how quickly fuel efficiency drops for certain models as highway speed increases. Obviously the faster you drive, the lower your car’s mileage, but when CR tested several different models it found that hybrids often experienced the steepest drops in fuel economy.
The Honda Insight was the biggest loser in the testing, losing almost 15 mpg after going from 55 to 75 mph. Hybrids were not alone in losing mpg. The Toyota Camry’s efficiency also turned sluggish once the needle crept up, going from 40.3 mpg at 55 mph, to 35 mpg at 65 mph and finally falling to 30 mpg at 75 mph.
The smallest differential between 55 and 75 mph turned out to be the least fuel-efficient model tested. The Mercury Mountaineer returned 23.8 mpg at 55 mph and fell only to 17.8 mpg at 75 mph.
Check out the results from all seven vehicles after the jump.
Tested: Speed vs. Fuel Economy (Consumer Reports)