Hypermiling and EPA vehicle efficiency estimates

Thanks for the welcome, Daniel!

I’m just getting settled into being back in Madison after a long road trip to Texas and back, during which my partner D was generous in driving the entire time, because I am a wimpy (and not particularly skilled) driver. We decided to drive partly to reduce travel costs, and partly to lower our carbon footprint.

To make the drive more interesting, my partner (during stretches of little or no traffic) decided to practice some hypermiling techniques. The idea of hypermiling is to use various driving practices, like pulsing and gliding in order to exceed the US EPA’s estimated fuel efficiency on one’s vehicles. Some of the techniques used by hypermilers are are relatively noncontroversial (like keeping your car maintained), while others (like drafting off trucks to avoid wind resistance) are much more controversial (and many hypermilers avoid them). According to D, some of these techniques are more “fun” (like thinking about ways to use hills to one’s advantage, and planning one’s routes to avoid using the brake as much).

So what’s this foray into hypermiling accomplished? In our blue ’05 Prius, we managed to get over 70mpg (EPA’s combined city/highway estimate is 46 mpg), which is still nowhere near the over 100mpg that some hypermiling marathoners have achieved. In his defense, D’s just starting. But he still might need more practice before being anywhere near competitive in the upcoming 2008 Hybridfest MPG Challenge.

One interesting thing is the relationship between hypermiling and official estimated fuel efficiencies for vehicles. If gas prices keep increasing, will more people adopt some of the more efficient driving techniques of hypermiling? After all, there’s already been studies that suggest that the amount of driving has decreased as a result of high gas prices. So what if the amount of driving not only goes down, but the actual driving is done with gas efficiency in mind? Is there a point at which the EPA must change its techniques for estimating vehicle efficiency to adapt to changing driver practices?

Update: As commenter Jon Garfunkel points out, there’s a lot more nuance to this.

The historically cheap price of gas in the U.S. (and vast size of the country, and commutes) hadn’t encouraged enough drivers to think about buying fuel efficient cars. So the Energy Tax Act of 1978 added the “gas guzzler tax” to push the disincentives up front to the purchase of a new car (strictly speaking, it’s assessed to the manufacturer, who duly passes it along in the total sticker price.) After all, even the most economically rational consumer can best weigh in the cost of gas today, not in the future, when they’ll be buying most of it.

There’s one twist: the gas guzzler tax is calculated based on the EPA mileage estimate. And the EPA in fact changed their formula a year ago. They changed it not to reflect the obscure hypermileage subculture*, but instead some more real world factors of like the A/C, quick acceleration, etc. And thus it increased the number of cars subject to the gas guzzler tax. If fellow liberals here are looking for administrative measures over the last eight years to celebrate, this could be one of them.

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5 Responses

  1. Welcome, guest blogger. (How do you write a post about driving/mileage without describing the car or the mileage? A little local color, please.)

    You’ve barely scratched the surface here, and a little Googling would’ve better tied this into the law.

    The historically cheap price of gas in the U.S. (and vast size of the country, and commutes) hadn’t encouraged enough drivers to think about buying fuel efficient cars. So the Energy Tax Act of 1978 added the “gas guzzler tax” to push the disincentives up front to the purchase of a new car (strictly speaking, it’s assessed to the manufacturer, who duly passes it along in the total sticker price.) After all, even the most economically rational consumer can best weigh in the cost of gas today, not in the future, when they’ll be buying most of it.

    There’s one twist: the gas guzzler tax is calculated based on the EPA mileage estimate. And the EPA in fact changed their formula a year ago. They changed it not to reflect the obscure hypermileage subculture*, but instead some more real world factors of like the A/C, quick acceleration, etc. And thus it increased the number of cars subject to the gas guzzler tax. If fellow liberals here are looking for administrative measures over the last eight years to celebrate, this could be one of them (notwithstanding the continuing ridiculous exemption of “trucks” weighing over 6,000 pounds– many SUVs. see more from a 2004 article by Andy Bowers in Slate going into length on the slippery weight of SUV’s, which can be heavy enough, or light enough, to qualify for a given law — “the ongoing hypocrisy that surrounds big SUV ownership.”)

    *The hypermiler’s bag of tricks also has, which you left out, turning off the engine while coasting on a highway. That’s illegal in some states. Driving closer to the speed limit is a more prudent measure. I managed to get 38mpg on my ’98 Civic going as close to the speed limit as I’ll admit. 🙂

  2. Steph Tai says:

    Hi there John! Thanks for the info! I knew that EPA had changed its mileage estimate to reflect additional factors like A/C, but I didn’t (though perhaps I should’ve) realize that the gas guzzler tax was tied into the mileage estimate.

    As for info about our car and our mileage, I had thought that I put it in on a subsequent edit of my post, but apparently I accidentally lost my edit. Oops! I’ll re-add it in.

  3. J says:

    So does anyone else think the idea of the “2008 Hybridfest MPG Challenge” is completely absurd?

    Let’s promote fuel efficiency and energy conservation by getting a bunch of cars together to drive around in circles!

  4. J says:

    So does anyone else think the “2008 Hybridfest MPG Challenge” is kind of absurd?

    Let’s promote fuel efficiency and energy conservation by driving a bunch of cars around in circles!

  5. Steph Tai says:

    It all depends on what ultimate effect it has, doesn’t it? If–through a ridiculous race–it encourages more people to adopt energy efficient driving methods in the driving that they already do, then I would argue it has a positive effect. If, however, it just encourages otherwise nondrivers to drive more, then it would have a negative effect. I honestly don’t know. Anecdotally, though, I’ve noticed that a lot of people I know have started deliberately driving more efficienctly after reading some of the recent news articles about hypermiling. But as more of an empiricist, I would want to see some kind of real social science study before passing much of a judgment either way. Mostly I’m just amused that the challenge is in my own town. 🙂