MPG Illusion: cash-for-clunkers bill should use the 1 Gallon Per Mile principle

The cash for clunkers compromise that was reached in Congress this week puts a lot of focus, understandably, on the miles per gallon rating of the cars in question. It's understandable because MPG is how most Americans think about fuel consumption. But, as we've discussed in the past, gallons per mile is another useful metric, and its proponents have updated their site with an article on Cash for Clunkers and the 1 GPM Principle.

What's the 1 GPM Principle? Well, it's the idea that:

a new car needs to save 1 gallon of gas every 100 miles compared to the original car to be carbon neutral. The new car will then offset the CO2 emissions from its own production in 70,000 miles of driving, which would occur in 4 to 7 years for most drivers.

Since the cash for clunkers proposal is designed to sell a lot of new cars and trucks, these vehicles will need to be built (well, there is a bit of a backlog available for now, granted), which will create more CO₂. The CO₂ emissions generated in the building process would be offset by the reduction in fuel use if the new cars are all at least 1 GPM (or should that be 1 GPHM?) better than the clunker that gets traded in. The trouble is that the way that the MPG requirements are set up in the compromise bill, specifically the markers for large light duty trucks, which only require improvements of one or two mpg, don't achieve carbon neutrality as written. A more approriate ruleset, the GPM propnents argue, would require vehicles that get 16 mpg or less to be replaced by a vehicle that gets 2 mpg better; 17-20 mpg vehilces would need to be swapped for something that's at least 4 mpg better; and anything that gets 21 mpg or better would need to be boosted by at least 6 mpg to get the vouchers. You can find the full details on the 1 GPM Principle here.

[Source: MPG Illusion via Green Car Reports]
Photo by KB35. Licensed under Creative Commons license 2.0.