It doesn't need to make sense as long as it's remembered, its not exactly rocket science to memorise a few basic numbers. Hence my complete inability to work in Metric, I didn't learn it so it makes no sense to me.
(Apart from working with Celsius)
Ah, but it is! There are basically three measurements used in the Aerospace Industry that everything pretty much boils down to: inches-pounds-seconds. I know there are some companies that prefer to use the Metric/SI systems for designing aircraft, but they're actually in the minority. Now, granted, I pretty much was taught that you science in metric up to the second year of college. The I got the engineering/design teachers and they tossed it all out of the window.
And my mile is 6076 feet long! And that figure is not random as some people may think.
And I really hate the bit about reducing mpg or l/km into an area measurement. Yes, you can do that (v = d^3, so v/d = d^3/d = d^2), but it destroys any practicality and meaning of the measurement. Oh hey, my car gets 0.000025 ft^2! Gee Bob, that's an awfully small trunk space. See, its even more useless than you're leading us to believe mpg is. There are measurements that crop up from time to time in engineering where you'll have something like inches per square inch, or seconds^2 per second. If you reduce that you end up screwing up the measurement and any practicality it had, not to mention earning the ire of the senior engineers.
MPG is a very easy way of contimplating fuel economy, as is Liters/100 km. Both show a direct correlation between 'how far I will go/how much I will use'. When most people are shopping based on fuel economy, they go for the highest numbers they can affoard. Sure, going from a Honda Civic (30/36) to a Prius (51/48) isn't going to save as much gas as going from Tundra (16/20) to a Fusion (23/33), but nobody shops like that.
The only thing you've proven is that averaging MPG ratings across a range of vehicles is a flawed way of creating legislation, thus CAFE is flawed, and we here in the USA already knew that!
(to avoid confusion, this post is responding to more than one person
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