What we're buying in terms of vehicles has changed greatly. The typical behemoth 8-cylinder SUV has given way to the more economical 4-cylinder car. That switch alone can represent a savings of $1,500 or $1,700 in gas over the course of a year.

The Toyota Prius is selling consistently after initially being seen as a curiosity item in the market. The Toyota Yaris, Nissan Versa and Honda Fit are also popular sellers. But does it make sense to ditch your huge vehicle and get one of the wundercars? Usually, it does not -- unless you're at the end of your natural buying cycle. But to prematurely dump your vehicle, the numbers probably won't work out in your favor.

If you are in a gas guzzler and want out, try buying a used gas sipper. This may not be "sexy," but you can always buy that new car smell in a can.

Then there's the safety issue. Clark was recently talking to someone who has an Expedition and raised this point to him. Today's smaller cars aren't exactly "econoboxes" like the Datsun B210 that Clark got new in the mid-'70s. That dinky-mobile came with no radio, no AC and the floor was just a vinyl sheet over the metal! But the truth is that you can't outsmart physics, so if the Expedition hits a smaller car…