I think of all the ways we could save fuel, a 10mph reduction on the open road speed (assuming of course we have compliance ... and we won't a lot of the time) is about the least effective.
I'm still convinced that this will amount to just a few percent ... while several times that amount is spent idling in the driveway, supermarket parking lots and stuck in traffic.
I like the idea that a gauge that tells you your real-time fuel economy become mandatory ... which reduces people's ignorance ... and we can't have too much of that. After all, waste is (mostly) caused by ignorance at many levels. I liked
jamesqf's comment about the reason people buy SUVs is following a current fad. Far too many people I know buy them and when you ask them, most shrug their shoulders and say "I dunno."
We deal effectively with those blighters and we're more than halfway there!
Cars WILL get more aerodynamic in the coming decade and with Cds of .28 and less, the real-world differences between 55mph and 65mph will all but disappear ... and it will take 2 more decades before the politicians, paid for by the insurance companies (who will be lobbying for a 45mph national limit by then), will even consider raising it back to 65mph so we can get across the state line in less than a 3-day weekend.
But, if the speed limit is reduced to 50-55mph, the benefits of aero are reduced ... and the incentive for the manufacturers to pursue them is also reduced. Hey! I want MORE aero, not less.
A lot said in this thread (plenty by me) is hunch and/or opinion. I'd still love some real-world analysis of the differences in a relatively modern car between 55mph and 65mph. In my '06 Civic, I bet it's 1-1.5 mpg based on trips I've taken. But that's just an educated guess.
