For Spring break we drove from Northern New Jersey to Carolina Beach,
North Carolina, where my brother lives. Just about everyone knows that
the faster you drive, the more gasoline you burn. But, we thought this
was a good time to put that principle to the test.
During part of the trip my husband tried to maintain a speed of 60-65 miles per hour (mph), and in other areas with higher speed limits, he pushed our Subaru Outback to 70-75 mph. Because our car has a digital readout of average miles per gallon (mpg), it was easy to see how we were doing. The upshot is that at the lower speed, we achieved 33 mpg. When we drove 10 mph faster, we achieved 29 mpg.
The entire round trip was about 1,700 miles (including stops at Williamsburg, Virginia, on the way there and Monticello, Thomas Jefferson's home near Charlottesville, Virginia, on the way back.) Most of it was highway driving. So, a simple calculation assuming an average gasoline price of $2 per gallon, suggests that we saved almost a penny for every mile we drove at the slower speed. If we drove the entire 1,700 miles at 60-65 instead of 70-75, it would have taken us a little longer to get to the beach, but we would have saved about $17. Not bad. But not quite as good as my neighbor, who has a Prius and says he averages 43 mpg when combining highway and local driving.