Except you have failed to even attempt to re-argue your claim that the perception difference between linear value changes and relative ratio changes make gpm a better way to express fuel efficiency than mpg.
There's nothing to "re-argue". It's an established case.
Which is the problem. You're not bothering to argue it because in your mind it's already "established" as true. Which is, at the very least, lazy as hell.
People, generally, compare MPG as if it were a linear measure.
Sigh... And, as I said earlier, they do the same damn thing with GPM
. The difference isn't whether one creates a different linear perspective relative to the actual ratio difference, but the directionality of that perspective change.
When shown the difference in the cost of gas per year, or whatever, they make different decisions.
Fine. But what differences? Doesn't MPG make people think they are getting more value at the high end then they actually are
? If our objective is to get someone to buy a car with higher fuel efficiency even when that efficiency only saves them a small amount of money personally, and presenting this as MPG instead of some other measure increases the odds that they'll buy that more efficient car, then isn't using MPG exactly what we should be doing?
You're correct that it can create a false perspective of the savings, but in this case, it creates a false perspective that actually increases the likelihood of the behavior we want (assuming, of course, that getting people to buy more fuel efficient cars is what we want). On the flip side, expressing it as GPM makes relative increases in fuel efficiency look smaller to the potential purchaser, and thus will statistically influence behavior *against* choosing to buy a more fuel efficient car.
The fact that's not really debatable here is that if consumers were actually given what you propose we should give them (real total cost of ownership over the expected ownership time period), consumers would be far far less likely to buy hybrid and//or electric cars. We trick them into buying those things by hiding the real costs and presenting them with a semi-false perception of savings in the form of mpg differences. We know that most buyers wont look at the increased cost for a hybrid versus regular version of a given car (for example), and then look at the MPG difference, then calculate how many miles they'll travel in an average year, and how many years they'll own the car, and calculate their savings and realize that they're not actually saving any money (or in some cases actually losing money).
So whether MPG is a good way to express that value or not depends completely on what we want consumers to do. There's no inherent "better" or "worse" method. Edited, Sep 16th 2013 6:45pm by gbaji