2011 Fuel Economy LabelsEnlarge Photo
Third, two-thirds of U.S. drivers don't understand that gas mileage is a non-linear scale: Improvements on the high end actually reduce fuel consumption much less than do improvements on the low end.
(Here's the math: Over 100 miles, improving from 10 to 20 mpg saves 5 gallons of gasoline; the "same" 10-mpg boost from 40 to 50 mpg saves just 0.5 gallons over the same 100 miles.)
This all adds up to a mess.
The stakes get higher when you realize that the EPA itself says a 2025 car will cost $2,600 more in real dollars than a 2011 model if carmakers choose the most cost-effective routes for boosting gas mileage.
Carmakers we've spoken to scoff at that estimate, saying the real cost might be double that--although crying wolf is a not-unknown tactic among auto engineers who (understandably) tend to dislike new rules in general.
This has all reignited debate over whether the CAFE and EPA window-sticker gas-mileage testing should be modified or updated.
It's always possible; the 2009 switch from "two-cycle" to "five-cycle" testing for gasoline vehicles added three more rigorous tests to the well-known "city" and "highway" ratings.
And such changes are more procedural than public.
President Barack Obama may have joined the head of the EPA to announce the new 2017-2025 CAFE requirements for 54.5 mpg.
But the rules and details of how those numbers are calculated are negotiated by government rule-makers and automotive engineers on the compliance side and rarely make it into the news.
Still, we can't help but be pessimistic that anything meaningful will change. So we can only leave you with the famous words, once again ..
"Your mileage may vary."