Imagine, if you will, a compact rear-wheel-drive hatchback that runs from 0-62mph in a very respectable 6.9 seconds. Not to shabby. Now imagine that this same car could average 45 mpg (US)! Not possible, you say? Au contraire! In other parts of the world where they don't just use gasoline to power cars, this is not an unheard-of possibility. One shining example is the BMW 123d, which was launched in Europe last year. Powered by a twin-turbocharged 2.0L four-cylinder diesel cranking out 204hp and 295lb-ft of torque, the 123d scores 45mpg (US) on the EU combined test cycle. For now at least, BMW isn't offering American consumers any of its four cylinder engines, but fuel system supplier Bosch has a fleet of European diesel vehicles that they use for promotional purposes.