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AutoblogGreen reader Jay S. read our recent post on gallons per mile (click the link to get caught up if you missed the discussion). He realized it's an idea he's been kicking around for a decade, and he sent in the following email, along with the charts in the gallery below:

Your Dec 16th 2008 article about a web site that lets you calculate how many gallons you use to go a certain number of miles reminded me of a chart I first made about 10 years ago. It is a plot of Gallons versus MPG for a few different total number of miles. If you look at the line for the number of miles that you drive in a year, you can see how many gallons that you will use for any particular MPG. This helps you determine what kind of car to buy.

When I first plotted this data, I was shocked that it wasn't a straight line. How could Gallons used for a given number of miles be a curve? Now, I look at it as a percentage thing. If I double my MPG, then I halve the total number of Gallons used.

Any engineer will tell you to get off the steep part of the curve, which means that you need to get at least 30 MPG, and really 40 to 80 MPG would really be doing good.

I think that this sort of study is why GM said it is more important to get better MPG in the big vehicles first, then work on the smaller ones. Making hybrid city buses was a great idea. Too bad the big SUV buyers don't really care.

Again, we don't want anyone to get the message that low MPG SUVs somehow burn less fuel than a 45 MPG Prius. It's just that when it comes to actually reducing fuel use in vehicles, there is a lot of possibility to be had at the lower end of the spectrum. Discuss. Thanks to Jay S.!

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