A real-world example of the effect of driving habits

Gratuitous Kari Byron photo courtesy of Discovery Channel
from their Hypermiling episode

As readers of this blog will know, I drive a Lexus CT 200h, a hybrid vehicle that's basically an upgraded interior and redesigned exterior wrapped around a Toyota Prius drivetrain. While I don't exert the maximal effort in hypermiling, eschewing, for example, the "pulse and glide" technique, I do utilize several of the techniques. Doing so has yielded an aggregate mileage, since the purchase of the vehicle three years ago, of 51.2 m.p.g. over the course of over 57,000 miles.

Early this year, a person I met through my Company purchased a CT 200h and agreed to track and log fuel economy and share the data with me. From the start, Arezoo mentioned that she'd not be willing to drive the way I do. In particular, she wasn't interested in maintaining a cruise controlled speed of 55 m.p.h. on freeways. She's mentioned 80 m.p.h. on a couple of occasions, though I don't know what she's able to average.

I was very interested in getting her reports so that I could have a comparison between normal driving in a CT 200h and my driving. The second set of results are now in, and Arezoo has recorded an overall fuel efficiency of somewhere just north of 38 m.p.g. (she is slightly less compulsive about recording data than I am). Thus, she uses about a third more fuel than I do to travel a given distance.

Image courtesy http://gunnip.com/blog/2012/04

Arezoo has burned about 208 gallons where, over the same course, ceteris paribus, I would have burned about 156 gallons. Her average cost of fuel was about $3.80, and thus she spent just under $200 more than I would have. One way of looking at this is that Arezoo judges her satisfaction in not driving the way I do to be worth at least $200 but, frankly, that's the wrong way of looking at it. From a purely economic perspective, the time that she saved was extremely likely to be worth far more than $200. The time cost of my 55 m.p.h. maximum has been a frequent subject of my posts.

Unfortunately, I have insufficient data to determine precisely how much time I lose, though I can approximate it and even determine it as somewhere along a curve in a three dimensional plot. I did such an approximation in one of the posts linked above, figuring that I lose in excess of 40 hours per year. But the governing set of equations is underdetermined and thus I can't nail it down. And I know I'm not saving the world, or even enough for retirement, but the nickels and dimes do add up.