A lot can change in one year. In May 2008, we had the idea to bring four frugal, fuel-sipping cars together to determine which was the most fuel-efficient and the cheapest to run, and which did better in specific driving conditions. While the EPA's fuel economy estimates are a good guide for determining a car's overall thirst for fuel, we wanted to do our own controlled testing to see how different types of cars performed in the real world.Indeed, the results of the original Gas Sipper Smackdown were telling, but the cars were hardly the sort most Americans could actually consider buying. The Smart Fortwo was frugal, but it was blown all over the windy desert and it didn't sip enough to counter its myriad compromises. The Ford Focus was one of the cheapest, most efficient American cars on the market, but it was an unimpressive rehash of a nearly decade-old design. The VW Jetta TDI was a used car and a previous-generation model since no non-luxury diesel car was then on sale. The eventual fuel-sipping winner, the Toyota Prius, was bound for a complete redesign.

Fast-forward to the summer of 2009 and things have really changed. Not only are fuel prices much different (especially diesel), there are more green-oriented vehicles than ever, with even more technologies introduced to get the most miles out of the least amount of fuel. We decided to revisit our cage match of fuel sippers, this time with a new and/or redesigned roster of green players to see how each did in our meticulous fuel economy testing.

We changed the name to Fuel Sipper Smackdown to reflect that diesel isn't gas and to leave the door open for future smackdowns when other alternative fuel technologies can make it to Las Vegas and back (sorry, no electric cars yet). The goal wasn't necessarily to determine a winner, but to find out the areas and environments in which each car excels and just how thrifty it really is.