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Miles Per Gallon Misjudgment
This week's Science has an article about why thinking about cars in miles per gallon (mpg) can be misleading. It may seem counterintuitive, but small increases at the lower end of mpg efficiency are more effective than larger increases at the higher end. In other words, increasing from 12 mpg to 15 mpg saves as much gas as increasing from 30 mpg to 60 mpg. The relationship is illustrated in the following graph from this AAAS news release:
The moral of the story is that small increases in the mpg of SUVs, trucks, etc. should not be dismissed, and that in making consumer decisions you are better off comparing the gas used per distance unit (e.g. 10,000 miles). (To calculate, simply take 1/mpg X 10,000.)
For more information, including a nice little video, see the AAAS news release.
5 comments:
Very nice. I thought this was going to be about the miscalculation of mpg---you know, where all the hybrids were said to get 60 mpg and turned out to only get 30. I guess this shows that that error wasn't such a big deal after all. {smile}
The nice thing about hybrids is they get their maximum mpg around town which is where most SUVs get their worst.
I've love a Toyota SUV hybrid for my next car. I've heard that if you ease up on accelerating around down you get 40 - 50 mpg. Sadly they are pretty worthless for actually going on anything rougher than a dirt road.
The problem with most hybrid is crappy mieage.
I wonder if congress would ease up on some of the safety restrictions which would get the weight down on cars so that a 50 mpg Geo Metro would be possible again.
If you're really willing to ease up on safety to trade up for better mileage, you could drive what I drive: a LeMond Tourmelet with dual density road slicks, clipless pedals, and Profile aerobars. Yeah, I know: it's not practical for families.
It still holds true that if I swapped my 30 mpg car with a 33 mpg car, I would spend 10% less on gas--the new car being 10% more efficient. The same is true if I increase the efficiency of my SUV by 10%. It just happens (assuming I drive the same mileage) that I spend 3x more gas on the SUV, so the total savings is larger (being 10% of a larger quantity of gas). As Mark Twain said, "There are lies, damn lies, and statistics."
Mark Twain did not say that. I DID!
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