Audi is making one of its smallest, most fuel-efficient vehicles even more efficient by outfitting it with a turbocharged diesel engine. How much more efficient? The new A3 2.0 TDI will reportedly get more than 40 mpg on the highway. While that’s not Prius-level mpg, the A3 is a much more substantial vehicle. It features a 2.0-liter 4-cylinder diesel engine that makes 140 horsepower and 236 lb-ft of torque, just enough power and oomph to feel downright peppy. Plus, the interior is quite fetching and well-equipped with leather upholstery, SIRIUS Satellite Radio and an auxiliary input for the stereo system, among other things.

Capable of driving up to 40 miles on battery-only power — using zero gasoline and producing zero tailpipe emissions — the 200C EV uses a small gasoline engine and an integrated generator that produces electricity to extend the driving range to 400 miles. It features goodies such as a “panoramic multimedia touch screen,” which takes the place of all switches and levers, and can be customized down to the desktop background. Based on a shortened version of Chrysler’s rear-wheel-drive platform, the 200C is unlike most electric vehicles in that it actually has style. Designers tell us that the 200C’s sweptback nose and “wind-cheating shape” make better use of the ENVI drivetrain.

This tré chic electric vehicle will be able to travel 150 to 200 miles on a single charge. While a purely battery-powered rear-wheel-drive performance coupe might sound like an oxymoron, the Circuit seems to work — at least on paper. Plus, using a tried and true platform, the Lotus Europa, Chrysler can save money and get this sporty EV on the road fast. The heart and soul of this two-seater is a 200 kW electric motor, lithium-ion battery pack and a sophisticated controller to manage the energy flow. The system develops an impressive 268 horsepower and a neck snapping 480 lb-ft of torque. Now, that’s an environmentally conscious sports car.

When Ford redesigned and re-engineered the midsize Fusion for 2010, the automaker wisely included its second generation gas-electric hybrid technology into the model mix. The result is a fully featured hybrid that is fast, comfortable and capable of 40 mpg in stop-and-go traffic. It truly redefines the hybrid. The Fusion Hybrid runs on 87 octane gasoline, but not too much of it given a 39 city/37 highway EPA rating. And it can go 700 miles on a tank of gas — or one trip to the gas station per month, perhaps — as a result.

Honda is setting its sights on the Toyota Prius with this four-door hatchback, which promises to be America’s lowest-priced hybrid. The 2010 Insight is powered by an electric motor, a 1.3-liter i-VTEC 4-cylinder engine and a continuously variable automatic transmission. Total output is 98 horsepower, with fuel economy ratings of 40 mpg city/43 highway. It also features an in-dash EcoAssist display with guidance and scoring functions that encourage efficient driving. The new Insight goes on sale on Earth Day, April 22, 2009.

What makes this particular hybrid unique from other gas-electrics is that it’s the first dedicated luxury hybrid — meaning that it hasn’t been spawned from a traditionally propelled Lexus variant. Even more impressive, the entire car was sketched to minimize impact on the environment, right down to eco-friendly interior materials. It features a few tricks such as variable valve timing, super-slick balanced internals and an exhaust heat recovery system that help the car offer 30 percent better fuel economy than the 2009 IS 250 RWD. That means this svelte four-door will achieve better than 35 mpg on the highway.

In Detroit were three cars that could represent a monumental culture shift for the luxury carmaker. The BlueZERO E-Cell is a plug-in electric vehicle that can drive approximately 125 miles on a single charge. The BlueZERO E-Cell Plus adds a small 3-cylinder gasoline engine and has a range of more than 370 miles, while the BlueZERO F-Cell has a fuel cell that converts compressed hydrogen into electricity. It can drive 350 emissions-free miles on one tank of gaseous hydrogen.

Already the undisputed leader in fuel-efficiency, the Prius gets even better gas mileage for 2010, gaining 4 mpg for a total of 50 mpg. While not spectacular, that’s still an almost 10 percent fuel-efficiency increase. And that fuel savings comes from a larger 1.8-liter gasoline engine and a vehicle with more cargo and legroom. The next-generation Prius goes on sale this spring, and it’s sure to be a winner right out of the gate.

Boasting a top speed of 140 mph while managing to get a claimed 55 mpg on the highway, this turbocharged 2.0-liter diesel concept puts out 180 horsepower and 258 lb-ft of torque. Coupled to a 6-speed double-clutch transmission, the TDI launches to 60 mph in 6.2 seconds. Vehicle weight is kept to a minimum (2,600 lbs) through extensive use of aluminum and other lightweight materials. When all is said and done, the BlueSport is smart and slick and proves that Americans and our government stooges should give diesel a second look.

Wagons are more popular than SUVs in Europe because of better gas efficiency, easier maneuverability in small towns and comparable cargo capacity. The new VW SportWagen is a taste of what Americans have been missing all these years. Its design is clean and functional, plus, it shines in highway driving. The 170-horsepower 2.5-liter 5-cylinder engine delivers good power for a vehicle this size, and with the 6-speed Tiptronic transmission it delivers better than 30 mpg fuel economy.