I was just watching a Modern Marvels episode about Aluminum. The process of extracting aluminum is pretty incredible... despite being the most common metal on Earth, but it's only been with the past hundred years or so that we've known how to make it in quantities. You basically take a bunch of dirt, mix it with some acids to create a foam of aluminum oxide, which you scoop up and dry into a salt-like powder (called alumina), then ship it to a forge where you pour the powder into massive furnaces and ZAP it with insane amounts electricity to separate out the oxygen, leaving pure molten aluminum. They then suck it up and pour into massive cubes, and if you want a sheet of aluminum - for an aircraft wing or Reynold's wrap - you then squish these blocks over and over again until you get the thinness you need. It's quite an astounding process that I never knew before.
One of the interesting things about the show was an interview with someone at a GM plant, talking about the weight savings that aluminum has allowed new sports cars to have. He gave this general rule of thumb which I thought was fascinating: For every 10% in mass reduction, you get approximately 8% gain in fuel efficiency. In other words, if you have a 3,000lb car which gets 25mpg, if you get rid of 300lbs somehow, you can get 27mpg.
Ever think about how much crap we carry around in our cars every day? I'm sure most of it serves a great purpose, but do you really need to carry around the jack and spare tire everywhere you go? Is all the plastic everywhere really needed? I wonder how much stuff you could strip out of a normal car, and still keep it comfortable and safe to drive?
There should be a startup out there to compliment the Tesla's of the world, no? Drive in Light Car Shops where you get an estimate of how much your car weighs, and a bunch of guys who can go through and and strip it bare, even going as far as replacing parts with lighter versions and doing air-resistance tests to add spoilers or whatnot. Imagine if you spent $500 at a shop like that, which stripped out god knows how much weight and you get a ton more fuel efficiency. With prices like they are now, it'd be pretty a great deal. People would probably need more reasons to rip up their car, though, so it'd need something like a certification which would let you drive in the HOV lanes or something... I'm not a car guy, so I'm probably not the first person to think of something like this, but I think it'd be cool.
I'm sure there's lots of things you can do to increase fuel efficiency like regular tune-ups, etc. but keeping our cars "light" might just work, hey? Just a thought... :-)
Update: Erik just pointed out this video he posted a couple weeks ago about a super-light Hypercar which doesn't give up size for fuel efficiency, and a link to VW's 1 Liter car prototype... which actually is one of those mini cars, but gets like 256 miles to the gallon. Cool!