EcoDriving 101 – Reducing Speed

by Tim Fulton on May 31, 2008

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This post is part of a series on basic ecodriving techniques, intended to expound upon a more basic description in order to make them more accessible as well as put them in the context of safety and practicality. 

Reducing your speed is one of the simplest things you can do to increase fuel economy.  Keep in mind I did not say it is the easiest thing to do.  I’ll admit it, most drivers like speed.  But, it is a very simple thing to do.  You just have to let off the pedal a little bit.

On average, a 5 mph reduction at highway speeds (ex. From 70 to 65 mph) will net you an 8% increase in fuel economy.  Of course this differs from vehicle to vehicle.  The larger your vehicle the larger you gain is likely to be.  Fueleconomy.gov says that you can see between 7 to 23 percent increase in mileage simply by slowing down to the speed limit.  What about even a little bit under the speed limit?

Here is a some testing done by MetroMPG.com comparing speed to mileage.

There is also the fact that the speed limit is also a much safer speed should speak volumes to the car buyers who buy large vehicles because they are safer.  If you really want to be safe, slow down to recommended speeds.  Road engineers design roads with these kinds of things in mind.

A little more on the technical side is the fact that aerodynamic drag increase exponentially with speed.  So, if you double your speed you have quadrupled your aerodynamic drag.  So, you can see small increases in speed can drastically increase drag.  Aerodynamic drag is also the main force your engine must overcome while traveling at highway speeds.

So, since your going slower your going to be late all the time now, right?  I sure hope not.  Slowing down from 60 mph to 55 mph on an hour trip takes you roughly 5 more minutes.  Anything less than an hour trip is going to be less and for that 8% fuel savings you are sure getting a good deal.

The last thing I will mention is stress.  How many times have you come up on a car going slower than you, and gotten all flustered as you try to find a way to zip past it?  Stress is a serious issue with people these days.  Your daily drive can be a great time to unwind after a stressful day at work.  Its a lot easier to unwind while just cruising along at the speed limit where you don’t have to worry about that slow poke who won’t get out of your way as you rush home.  Take a few minutes longer to get home and feel better at the same time.

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Image: yr0gerg @ flickr, under CC

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{ 6 comments }

1 Matthew June 4, 2008 at 10:49 am

I have been wanting a graph of speed vs. fuel economy for my ’03 Mazda Protege LX forever…exactly like the one in this article.

Is there somewhere on-line I can generate one of my own?

Thanks,
Matthew

2 Shane Labs June 5, 2008 at 3:26 pm

There’s a calculator that shows this exactly this effect over at http://www.mpgforspeed.com/

Great post, very good info….

3 SpongeBob June 8, 2008 at 3:15 pm

I slowed down. Its so much more enjoyable going a bit slower! And trying to ‘hyper mile’ is quite a cool game to play against the wife. It used to be who can get there the quickest, but now its switched to who can get the best fuel economy….

4 matthew payne July 6, 2008 at 3:07 pm

sorry 55 is too slow….

5 Nick July 10, 2008 at 4:48 am

I discovered years ago that rushing around didn’t get me where I was going a whole lot quicker.

I stopped trying to drive everywhere at 20mph over the limit, and just went with the flow (at or slightly under the speed limit)
Then I noticed other people driving the way I used to – like they’re on a mission – passing me in a hurry, then having to stop at the next intersection a mile down the road, or slow down behind a bus or a truck, with me right behind them.
I find it really relaxing to just sit behind a truck and bimble along without the stress of trying to overtake or worry about the goon behind who’s trying to push everyone out of his way.

6 Anne May 28, 2010 at 4:18 am

Even us old gals can get into this. I bought a Nissan Frontier Pickup 8 years ago at age 61. With retirement and my beloved pickup’s 19 to 21 mpg, I had to save money. Without any fancy monitors or anything, I started developing a system of driving that I now know is hypermiling. (Thank goodness I prefer a straight shift!) I now get an average of 29 to 31 mpg. I also love the more relaxed drives and the fun of figuring out the most economical routes and driving technics. I have hopes of one day getting 35 mpg. I am amazed and delighted to find out that I am not alone and that there is a place where I can find new ideas.

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