2007 Lexus GS 450h
Hybrids can be dull, but the GS 450h is the riotous, self-indulgent yang to the Toyota Prius's quietly responsible yin. It's an expensive, sumptuously

Alt Fuel: Hydrogen

Optimists Say: Hydrogen fuel cells power vehicles by producing an electrochemical reaction between hydrogen gas and oxygen. The only by-products? Electricity and water. Pessimists Say: With just 36 hydrogen fueling stations in the U.S. and auto companies lagging behind on the technology, it'll likely be 2018 before we see these clean cars on the road. Plus it takes a significant amount of energy to produce hydrogen in the first place (from water, biomass, coal, or natural gas), making it imperative to improve the supply chain if hydrogen is to become a widespread alternative. Learn More: www.hydrogenassociation.org —M. M.

appointed luxury sedan that accelerates more wildly than a Porsche Boxster S. Ironically, the high-octane performance comes from a devilish twist in the hybrid-drive system that it largely shares with the Prius. In addition to propelling the car at low speeds, the electric motor acts like a turbocharger, transforming the 3.5-liter V6 into the equivalent of a V8, with a total of 339 horsepower. The car's fuel economy won't win any green awards—28 mpg on the highway—but that's a figure competitors from BMW and Mercedes aren't likely to duplicate without a strong wind at their tails. The GS 450h is outfitted with typical Lexusian gadgetry, from heated front seats to side-view mirrors that swivel down so you can see the curb while parallel parking.

MSRP: $54,900 As tested: $61,149 Hybrid premium: $3,500 MPG: EPA, 25 city/28 highway; our average, 23 Decrease in annual greenhouse-gas emissions from comparable gas-only model: 5.4 percent Pros: Blistering performance, luxury appointments Cons: Fuel economy looks good only when compared with the luxo-barges in its class, pricey