Mercedes-Benz E250 Bluetec concept

Europeans think nothing of putting a four-cylinder engine in a $50,000 midsize luxury car on account of fuel being so expensive. Now Americans are getting - possibly - the same option if this Mercedes-Benz E-Class concept becomes reality here. This is really two bets in one for the U.S. market: a small engine of four cylinders and 2.2 liters displacement powering a big, expensive sedan; plus a turbo diesel not gasoline engine with 204 hp and 369 pound-feet of torque, which for those not conversant with tech jargon like torque means enough grunt to tow a 747 away from the gate whether the pilot is ready or not. As the freshest midsize luxury sedan, the E-Class with any engine is 2009's top choice for moderately high bucks transportation for four, over the aging BMW 5 Series and the Audi A6. This is my pick for the most important green car of the show.

Fisker S (Sunset) concept

This is the perfect auto show green car: sexy, expensive, fun to look at, impractical, and oh so green. The Fisker S (for Sunset) is a concept convertible plug-in hybrid, meaning it runs on batteries and also has a combustion engine for when the batteries give out. The price is estimated at $87,000 when it goes into production, which is slated for later this year. Impractical? You'd need to live a long life to for the energy-savings difference between the Fisker S and, say, a Porsche Boxster, to catch up to the price differential. But as with the Boxster, it's about more than basic transportation. It's about how you see yourself, and others seeing you.

Chevrolet Volt

Chevrolet says it's on target to deliver the Volt to buyers late, late in 2010. Maybe the Volt will be the object that descends the Times Square ball tower at 11:59 p.m. If GM can pull this off - provide a vehicle that runs 30 or 40 miles on batteries, then a couple hundred miles more on the tiny combustion engine and a single tank of gas- it's a huge step forward for alternative energy vehicles. It's going to be cramped inside, especially in back, compared to a Toyota Prius.

Honda FCX Clarity Fuel-Cell

The Honda FXC Clarity has been kicking around auto shows for two years now and you can lease one if you live in parts of Japan or Southern California. What brings the hydrogen fuel cell Clarity back to prominence is its recent recognition as World Green Car of the Year. When you combine hydrogen with air to produce electricity with no emissions other than water vapor - excluding any emissions from wherever the hydrogen was generated - that's about as green as you can get. Nobody knows if hydrogen cars will ever be energy-neutral, but it's a bet worth making for our long-term future.

BMW X6 Hybrid

BMW is the master of giving impractical cars a practical bent. The BMW X6 Active Hybrid is one such vehicle, that charges you extra for less back seat headroom and cargo capacity than the X5. (But it still carries far more people and luggage than a 2+2 coupe.) This will be BMW's first two-mode hybrid, meaning it can run on battery power, gasoline combustion engine, or both. The jointly developed transmission/electric motor (but not the engine - BMW would never farm out that work) is derived from a consortium of BMW, Chrysler, Daimler, and GM. On three-ton GM SUVs, it has helped them top 20 mpg around town. With the X6 weighing 2.5 tons, buyers might see 25 mpg. Both the X6 strong hybrid and BMW 7 Series mild hybrid (electric propulsion supports the 7 Series gasoline engine; it never runs on battery-power alone) are due out late this year. As with the Mercedes-Benz hybrid announcements, these are important because Germany's green offerings have tended to be clean diesels.

GM/Segway PUMA

The original Segway convinced a gullible Time magazine that the world of transportation was in for a revolution. Or at least a paradigm shift. Instead, the world of airport security cops patrolling airport concourses was in for a revolution. Towns haven't spent taxpayer dollars to create Segway-only paths and aren't likely to; golf carts remain the way to get around gated retirement communities. The Project PUMA (Personal Urban Mobility & Asscessiblity) seated-not-standing vehicle is a self-balancing, two-person rickshaw with an electric motor and lithium-ion batteries replacing the coolie. See Jamie Lendino's PUMA report for details. This is a prototype that GM says could be built for less than the cost of a small car (not hard when you see how Spartan this is). Like hydrogen cars that have their skeptics, PUMA is a welcome addition to the possibilities for alternative vehicles, some of which will never happen. GM's cash burn isn't so severe it can't fund a couple longshots.

Chrysler 2000 EV

It's a prototype green car that can go 40 miles on battery or a lot farther when a small gasoline engine kicks in - just like the Chevrolet Volt but with more interior room. And it's a technology testbed for uconnect, Chrysler's telematics, emergency crash notification, Bluetooth, TV over the Internet, and-so-forth services. The concept is rear drive but since it's a concept, it could be front drive if that's what the market wants and if Chrysler taps Uncle Sam for enough money to bring this to production. Unlike the Chrysler 300, the design is more mainstream and people under six-feet tall could actually see out the side windows. Nobody knows if the 200 EV really will go 40 miles on batteries, or if that's what Chrysler says since that's what Chevy says.

Toyota Prius

Almost ready to go on sale, the 2010 Toyota Prius is pretty close to a midsize mainstream car that, oh by the way, is a hybrid that gets 50 mpg in town and out on the highway. When I drove an early production Toyota Prius, I got nearly 60 mpg. So much depends on Prius pricing. If it matches the currently cheaper but smaller Honda Insight hybrid, then Prius is the obvious way to go. The 10 mpg advantage the Prius offers really isn't all that much (in dollars) better than the Insight, except for bragging rights. And it's the odds-on favorite to be someone's, probably everyone's, 2010 green car of the year.

Mercedes-Benz ML450 Hybrid

The mpg numbers aren't much compared to a Prius, but those already inclined toward a medium-large SUV will find comfort getting 21/24 mpg (city/highway) rather than the 15/20 of the gasoline ML350 V6. Or you could buy a diesel Mercedes SUV and get even better mpg; I saw 28 mpg in the bigger Mercedes-Benz GL320 diesel. The ML450 hybrid is due out in December.

Mercury Milan / Ford Fusion

This roomy midsize car tops 40 mpg, same as the much smaller Honda Insight. Both the Milan (shown) and nearly identical Ford Fusion are high-mpg hybrids with plenty of room, attention to cockpit fit and finish, a choose-your-level-of-complexity energy monitor, and Ford's perfectly priced (free on most models) Sync Bluetooth and audio system. Toyota's advantage with its 50 mpg Prius works out to just $204 per (12,000-mile) year.