Cash-for-clunkers gallons-per-mile calculations

By Felix Salmon
May 8, 2009

Ryan Avent and the MPG illusion both examine the “cash-for-clunkers” bill from the perspective of how much in the way of carbon emissions will actually be saved when someone takes advantage of it. But there are a few sums missing in these posts, so I thought it would be worth filling them out. Here’s Ryan, for instance:

For passenger cars, the incentive is reasonably ambitious: those moving from less than 18 mpg to better than 22 mpg qualify for $3,500 for a four mpg improvement and $4,500 for a 10 mpg improvement.

But standards quickly decline as you move up in size. For SUVs and light trucks one qualifies simply by moving from below 18 mpg to above 18 mpg. A $3,500 voucher is available for an improvement of just two mpg, while a mere five mpg improvement gets you the full $4,500 available.

The full table is here, but only in MPG form. In terms of gallons of fuel used per 100 miles, things look a bit different. Here’s how things work out in useful gallons per mile, rather than silly miles per gallon.

To get a $3,500 voucher by trading in a car, you need to move from 18mpg to 22mpg — which is an improvement of 1 gallon per 100 miles.

To get a $3,500 voucher by trading in a small SUV/truck, you need to move from 16mpg to 18mpg — which is an improvement of 0.7 gallons per 100 miles.

To get a $3,500 voucher by trading in a large SUV/truck, you need to move from 14mpg to 15mpg — which is an improvement of 0.5 gallons per 100 miles.

To get a $4,500 voucher by trading in a car, you need to move from 12mpg to 22mpg — which is an improvement of a whopping 3.8 gallons per 100 miles.

To get a $4,500 voucher by trading in a small SUV/truck, you need to move from 13mpg to 18mpg — which is an improvement of 2.1 gallons per 100 miles.

To get a $4,500 voucher by trading in a large SUV/truck, you need to move from 13mpg to 15mpg — which is an improvement of 1 gallon per 100 miles.

So Ryan’s absolutely right: the criteria for SUVs are much weaker than the criteria for trucks. Why do you need to improve by 3.8 gallons per 100 miles in order to get the $4,500 voucher on a car, when you can improve by just 0.5 gallons per 100 miles in order to get a $3,500 voucher on a large truck? It doesn’t make a lot of sense.

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Comments
13 comments so far

All of these numbers should include part of the carbon emssions cost of building a new car or SUV. I have some doubt you will actually reduce emissions at all.

What if I want to move from 23 mpg to say 35 mpg and buy a hybrid – ??

I am still moving upward and that means reduction of environmental pollution ?

Thanks

Posted by Sree | Report as abusive

What happens under the following situations?
a) you trade in a car and move from 19mpg to 23mpg?
b) you trade in a car and move from 25mpg to 35mpg?

Posted by JAMG | Report as abusive

The largest reduction of environmental pollution could be achieved by trading in a gas guzzling truck for a hybrid car. That doesn’t appear to be allowed.

Posted by Bert Crist | Report as abusive

If you are currently being “green” and driving a car that gets better than 18 miles per gallon, YOU GET NOTHING.

Posted by Bill | Report as abusive

One of the big aims of the bill’s backers is to encourage people to buy new vehicles, since sales have been in the toilet. There isn’t that much improvement available, in trading an old truck for a new one – you are, after all, hauling tons of metal around – so they are going for what’s possible there. The less-gasoline-used benefits are, somewhat, window dressing.

Posted by dave.s. | Report as abusive

What this plan fails to take into account is that older cars may be operating way below their rated milage. I’ve got a 19 year old small pickup with 200K miles that was apparently rated at 22 MPG highway, 12 is the best I’ve seen out of it.

The truck seems like one they would want to replace, but at the rated milage it will not qualify.

Posted by Chuck | Report as abusive

It’s stupid to think that I need to keep driving my 1986 Ford because it GOT 18mpg’s in 1986 and, therefore, doesn’t qualify for a voucher!

It doesn’t seem so insignificant when you look at the percentage increase (not that this will sway anyone who believes the claptrap post above).

To get a $3,500 voucher by trading in a car, you need to move from 18mpg to 22mpg — which is an improvement of 22%.

To get a $3,500 voucher by trading in a small SUV/truck, you need to move from 16mpg to 18mpg — which is an improvement of 12.5%.

To get a $3,500 voucher by trading in a large SUV/truck, you need to move from 14mpg to 15mpg — which is an improvement of 7.1%.

To get a $4,500 voucher by trading in a car, you need to move from 12mpg to 22mpg — which is an improvement of a whopping 83%!

To get a $4,500 voucher by trading in a small SUV/truck, you need to move from 13mpg to 18mpg — which is an improvement of 38.5%.

To get a $4,500 voucher by trading in a large SUV/truck, you need to move from 13mpg to 15mpg — which is an improvement of 15.4%.

Posted by Sully Fick | Report as abusive

So the idea is to punish those of us who have always been environmentally conscious and to reward those who formally purchased gas guzzlers? brillant.

Posted by JimS | Report as abusive

Exactly… Environmentally irresponsible drivers are being bailed out just like the financially irresponsible homeowners and banks. While those who have been responsible all along get nothing but higher taxes.

Posted by Thanks Comrade | Report as abusive

This is a really good idea, except it needs some fine tuning. Good, in that it recognizes that our domestic manufacturing is in desperate need of a boost or we’re not going to be able to pay our way in the future as a nation, and also good in that the biggest contributors to fuel usage and climate charge are the worst gas guzzlers but at the same time a large family can’t just all pile into a Smart Car. And in need of fine tuning in that there ought to be an opportunity for those with more economical vehicles to save something as well. It ought to be based on percentage reduction in fuel consumption. And it ought to contain a sweetener for domestic production. The government calculates both down to the percent, so it should be easy to calculate a formula. The more domestic components and assembly work, regardless of manufacturer, and the more fuel saved, the bigger the reward.

Posted by DBX | Report as abusive

What if I own a 1985 Volvo that supposedly gets a combined 20 MPG according to fueleconomy.gov, but is definitely polluting the environment due to the age of the car? Shouldn’t it matter that my car leaks fluids and is definitely polluting the environment even if avg fuel economy according to the website is 20MPG?

Posted by Rebecca | Report as abusive
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