Energy Tip #18: Follow the speed limit

speeding.gifFrom James Dean to The Fast and the Furious to Herbie Goes Bananas, racing has long been an iconic Hollywood staple in which the ‘pedal to the metal’ mentality is consistently glorified. However, if you like to leave fellow drivers in you wake, you might be interested in knowing that you can save $17-67 (plus a few hundred bucks in speeding tickets) by simply obeying the rules of the road. Going above the speed limit, particularly at the higher end of the spectrum, will drastically reduce your fuel efficiency.

Speeding causes extra air resistance on the vehicle and speeds above 60 mph can especially be a drag. The U.S. Department of Energy estimates that for the every 5 mph above 60, the decreased fuel efficiency is the equivalent of paying a $0.20 surcharge on each gallon. The costs can quickly add up.

Let’s take a look at the numbers…

Avg. MPG: 19.6
Avg. MPG above the speed limit: 15.1 – 18.2
Avg. miles/yr. above speed limit (est.): 2,000
Increased gallons of gasoline used: 7.8 – 30.4
$ saved by not speeding: $17 – 67
CO2 saved by not speeding: 152 – 590 lbs

Last week 151 people pledged to wash and rinse in cold water (Tip #17). At 1,281 lbs of CO2 per pledge, voters reduced a very healthy 193,431 lbs of CO2. This is a fairly easy tip, and one that can be passed along to receptive friends.

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  1. Al - November 8, 2006

    We have to weigh the value of our time against the excess fuel cost from driving fast. Luckily most of our long distance trips are in MT and ID, where the speed limit is 75. If we drove 65 our gas mileage would increase by 3-4 mpg, but our normal 500 mile trip would be very long and very boring.

  2. Dwight F. Collins - November 8, 2006

    granted. but for a trip that long, an additional hour of travel versus the contribution you make to conservation should be considered. With Ipod’s and portable ps2’s, and DVD players, it seems that the boring and lengthy aspects of the trip might be significantly reduced. Peace

  3. Donald Baxter - November 8, 2006

    Make a compromise, Al. Drive like your grandmother in town to compensate for the high speed trips our west. I’m always astounded by how many people rush to the next red light. I’m always catching up to the people who passed me and I ride a bike to work every morning. Cars pollute more at idle, besides.

  4. Debby Detering - November 8, 2006

    Besides being concerned about the environment, my husband and I are older drivers. We live in California, drive often on roads in such poor condition that even the speed limit is too fast for conditions, yet when we drive the speed limit it seems everyone else whizzes past us. No wonder both our air quality and the local accident rate are abysmal, and car insurance (on an accident-free record) is twice what it was in another state.

  5. Adam - November 8, 2006

    The time differences over long trips may encourage you to consider speeding, but most highway trips aren’t 500 miles long. Consider a moderate highway commute of 20 miles. At 80mph it would take 15 minutes. At 60mph it would take 20 minutes. All of that ridiculous speeding, weaving, and cop avoiding, and you’ve managed to save yourself five whole minutes. Please don’t pretend you couldn’t have just left five minutes earlier or arrived five minutes later. The shorter the trip, the smaller the time saved by speeding. The extreme example would be akin to that put forth by Donald, where speeding 100 yards to the next light has really only saved a few seconds.

    I have completely revamped my driving habits to focus on reduced speed and acceleration. My mileage is through the roof, my gas expenditures are reduced, and it’s really quite peaceful over in the right lane. Leave the left lane for the self-important maniacs who have to rush home to sit and watch TV.

    Time is valuable, but so is our planet.

    [Ed. note — in case there’s any confusion, this comment was NOT posted by the Adam who is an author at Terrablog.]

  6. David M - November 8, 2006

    My car shows an estimate of my current MPG, and yes, I definitely see a difference between 75 and 65 MPH. But try telling that to the vehicle pushing against your back bumper!
    I’ve found that, just by easing up a bit (both accelerating slower and braking/coasting sooner and less hard) improves mileage a lot. Best done when there’s no one behind you, of course.

  7. Chad - November 8, 2006

    After a few quick calculations, and you can derive a quick rule of thumb – multiply the price of gas by four, and that is how many dollars in gasoline you are saving for each hour of additional driving time that you incur. Most of us value our time much more than $10/h, so driving slower to save gas is not an efficient use of our time (and even more so if there are passengers). Rather than driving slower, get to work quicker, make a few extra bucks, and buy a Terrapass, solar water heater, or insulation.

  8. Donald Baxter - November 9, 2006

    I’d rather not judge the value of my time against the environment. Drive slower AND do all those other things.

  9. Diogenes - April 1, 2007

    Lets cut to the chase, “Speed = Greed” plain and simple.

  10. kat - July 11, 2008

    My car Chrysler PT Cuiser. Avg 24mpg on freeway, I am driving 80-90 miles/hour every time I can and still have at least 23mpg.
    I will not slow down no matter what!