It may not be fun, but we all know that slower driving speeds are a good way to maximize fuel economy on the highway. To help prove this point, Consumer Reports did a series of tests to see exactly how much better a vehicle's fuel economy is at varying speeds. CR used five cars (Honda Accord four-cylinder, Toyota RAV4 and three different Ford Fusion models), which were each tested at 55, 65 and 75 miles per hour to determine the variations in fuel economy.
Not surprisingly, each car surpassed its fuel economy estimates at the slowest speeds. Econ for each also drops off considerably as the speeds increased. Driving the extra 20 mph will knock about an hour off of a 200-mile highway drive, but the test shows that it will also burn an extra two gallons of gas. Calculated out for a 1,000-mile road trip, we see up to 10 gallons of gasoline could be wasted. It would have been interesting to see how a diesel performed in this test, or even how Texas' new 85-mph toll road plays into this topic.
A couple interesting side notes in this tests include the four-cylinder Accord getting the same highway fuel economy at 55 mph as the Fusion Hybrid. Still more impressive, even at 75 mph, the Accord was still getting close to its EPA numbers (depending on which transmission was being used).