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The Miles Per Gallon IllusionJuly 7, 2008
In this issue: Gas Efficiency, Green Tech, Maker Shed Sale
Makers,
As gas prices here in the USA hit all-time record highs, folks start to look for ways to improve gas mileage, cut costs, and calculate savings on their vehicles. On the MAKE online site, we try to post some of these clever hacks as well as insights into what can actually work. This week we take a look at "The miles per gallon illusion (Miles per gallon vs. gallons per mile)."
Also, be sure to check out our "green" section on MAKE -- it's literally blooming with Maker-made green tech from around the world! "Don't buy what you can make, don't make what you can find!" No matter what, keep on making!
http://blog.makezine.com/archive/green/
Finally, don't forget to check out our July Special at the Maker Shed!
http://www.makershed.com/
Here's how it works:
* Choose one of the selected $10 T-shirts (no substitutions) and add it to your cart.
* Select another product or products that total $30 or more.
* Enter in code "T4ME" at checkout and your $10 T-shirt becomes FREE!
Cheers,
pt
Phillip Torrone
Senior Editor
MAKE Magazine
From the MAKE Blog
The miles per gallon illusion (Miles per gallon vs. gallons per mile)
Bunnie has an interesting write up about AAAS's Science publication "The MPG Illusion" he writes...
Here's an interesting question.Suppose you had a household with two cars, and each car needs to be driven 10,000 miles per year. One car consumes 34 MPG, and the other car consumes 18 MPG. Since gas is expensive, you want to replace one car. Because of utility constraints, you have two choices:
Which car replacement would save you the most gas?
- Replace the 34 MPG car with a 50 MPG car -- a 16 MPG improvement
- Replace the 18 MPG car with a 28 MPG car -- a 10 MPG improvement
Normally, I consider myself not bad with quantitative comparisons like this, yet initially I picked the answer of replacing the 34 MPG car with the 50 MPG car based on the superior 16 MPG improvement. Another seemingly more analytical approach also leads to the same conclusion: 50 + 18 MPG giving a 34 MPG household average seems more efficient than 34 + 28 MPG giving a 31 MPG household average.
This very interesting article in Science, "The MPG Illusion" by Richard P. Larrick and Jack B. Soll at the Fuqua School of Business in Duke University (Vol 320, June 20, 2008, p. 1593), points out the mathematically obvious truth that gas used per mile is inversely proportional to miles per gallon, which means that you have a steeper slope at lower MPG ratings, and diminishing returns at higher MPG ratings.
More @ Bunnie's site. At first glance it seems counterintuitive, but here's an interesting thought...
Relatively small MPG improvements in the most gas-hungry vehicles pay off greater than larger improvements in already efficient cars (hence, it does make sense to offer tax breaks for modest improvements in SUVs versus tax breaks for hybrids, which typically replacing already gas-efficient sedans).Ok makers, what do you think? Post up in the comments!
