Continuing with my evaluation of how to be earth-friendly and such, I wanted to see how speed affects gas mileage. 55mph has been touted for years as the most efficient speed in terms of gas consumption, so I decided to try driving a whole tank at 55mph (while commuting on roads with appropriate speed limits, of course).

Except I couldn’t do it. I can drive 60mph, but 55mph seems Way Too Slow. Ridiculous, driving-like-a-grandma slow. Every-single-person-on-the-highway-is-passing-me slow. (Caveat: the major highway I take has a 65mph limit – then I have the joy of driving through NJ, where peeps drive WAY fast for a 50mph zone.) I think it was actually more dangerous too – I spent a lot more time checking my speed, reducing my attention to the actual driving. At 60mph, the rpm was a hair under 2500 and the engine sounded right, and I could drive more normally.

The car in question is a 5 speed manual Subaru Forester, acquired primarily as a reliable, snow-friendly family vehicle. Prior to this test, I usually drove about 65mph and got roughly 25mpg (a guesstimate). At 60mph, the mpg bumped up to 28.5 – not too shabby. With a gas tank of almost 16 gallons, that’s almost 60 more miles, enough to commute to work one-way. And the difference in commute time is only about 5 more minutes.

Another plus is that going that speed means I rarely need to pass anybody and am enjoying a way more leisurely ride. I’ve been known to be a, shall we say, opportunistic driver, and I’m finding these leisurely rides to be less stressful. So I drive along calmly, listening to an audiobook, a podcast or belting out some tunes (my stay-awake-at-night trick). I’ll keep shooting to drive a whole tank at 55mph, but only if I can do it without having to pay constant attention to my speed. Have you tried anything like this?