Gallons per mile
There are lots of very difficult, nuanced issues in politics — issues where two intelligent people could disagree, have an intelligent back and forth for hours, and still come out with totally intact, cogent views on the topic. These are often fundamental questions about the very way our country works. But there’s another kind of issue. There’s the kind of issue where there is just an obvious correct decision, with very little room for intelligent discussion. Sometimes these issues are incredibly important, but more often they are small and just slip by, because only a handful of people is involved in the relevant decision, and they didn’t realize what they were doing. These issues annoy me the most, because, however minor they are, there’s no excuse for failing to do the obviously correct thing.
The way we measure fuel efficiency is one of these dumb things. Using miles per gallon is really misleading. It can make tiny gains seem huge, and huge gains seem tiny. Let’s take two totally hypothetical vehicles. One one hand you have a hybrid car, which gets 40 mpg, and you convert it to a plug-in hybrid, which gets 100 mpg. On the other hand, you have a very inefficient small truck, which gets 10 mpg, and you put in a more efficient engine, pushing it to 15 mpg. It seems like the former improvement is better. It’s a 60 mpg improvement rather than a 5 mpg improvement. It’s a 150% improvement rather than a 50% improvement. Nevertheless, if we assume both vehicles are driven 1000 miles, the hybrid goes from using 25 gallons to 10 gallons, saving 15 gallons, where as the small truck goes from 100 gallons to 67 gallons, saving 33 gallons. The gain from improving the truck’s efficiency is massively better than the gain from improving the car’s.
This is a general mathematical fact. The inefficient vehicles are the ones using lots of fuel, and small changes in their mileage are large percentage changes, so very small mpg changes can save a lot of fuel. The super-efficient cars use very little fuel anyway, so even massive improvements can’t save that much. Consumers, obviously, think about mileage in the units that it’s given to them in, so they value it in an irrational way. (Science Pundit has a great post about this.) It would make a lot of sense to change to gallons per mile (or per 1000 miles) and get consumers thinking more rationally, but I can understand the reluctance. The switch to a new unit takes mental adjustment, and it’ll take a while for consumers to get a good handle on what counts as “good” or “bad” mileage, meaning they’ll probably take efficiency into account less during that unit transition. (Interestingly, it seems that this is already frequently done in many other countries. Sociological Images posts this video that shows mileage in L/100km.)
What really makes no sense is using mpg in regulation. US automobile efficiency is regulated by the CAFE standards, which mandate a minimum average mileage for the fleet of vehicles produced by each manufacturer. The problem is, by using miles per gallon, rather than gallons per mile, the economic incentive is to produce more super-efficient hybrid small cars, whereas much bigger gains could be made through smaller improvements to the worst vehicles. Adding 3 mpg to a hybrid doesn’t cancel out a loss of 3 mpg in a pickup truck, but that’s how the standards work. You could easily pick the new required average to be no more or less stringent than the current one — it would just be more intelligent. If anything, it would help US manufacturers over Asians ones, since it’s the Asian manufacturers that are producing the small, hybrid cars.
There is only one intelligent argument I can think of against this change, which is that these super-efficient cars are the ones that are pioneering technologies that will push down to all vehicles sooner or later. This might be true, but I doubt it’s fundamentally necessary. (It’s easier to put a more advanced engine or a battery in a big vehicle than a small one.) Maybe you can make an argument that this over-counting of gains for small cars is a way of subsidizing the technological innovation behind them. I don’t really buy that, though. A change in the regulatory measures seems obviously good.
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[...] else comes to mind”. (One post of theirs from earlier this month that I particularly enjoyed: Gallons per mile, which examined whether miles per gallon is the most appropriate way to measure a car’s [...]