Photo gallery: Greenest of the green: The cleanest hybrids of 2007

The 2007 Ford Escape Hybrid is the only full hybrid vehicle to sport the Blue Oval. It relies on a 2.3-liter, four-cylinder engine, mated to a continuously variable transmission (CVT) and assisted by a 70-kilowatt electric motor. The hybrid Escape's price has gone down for 2007, making it a better value relative to its V-6-powered gasoline equivalent. Look for an upgraded cabin in the 2008 model.

Toyota's pioneering hybrid has seen a whole automotive segment grow up around it. With its Hybrid Synergy Drive (HSD) drive train comprising a 1.5-liter gasoline engine and 50kW electric motor, the Prius set the the standard for parallel-series hybrids. Under the revised EPA gas mileage ratings designed to more accurately reflect real-world driving, the Prius has dropped from a city rating of 60 mpg to 48 mpg. Nevertheless, it is still one of the most efficient cars on the road. It is rated as an advanced technology partial zero emissions vehicle (AT-PZEV) by the State of California.

The Mariner Hybrid shares its platform and Toyota-inspired power train with the Ford Escape Hybrid. Unlike its Escape counterpart, the Mercury Hybrid is available only as an all-wheel-drive vehicle. Updated EPA figures rate the Mariner Hybrid at 28 mpg city and 27 mpg highway.

Unlike Toyota's hybrids, Honda's hybrid models cannot run only on electric power. The Accord Hybrid relies on Honda's Integrated Motor Assist, which augments--rather than replaces--the car's 3-liter V-6 gasoline engine. Due to its relatively large engine, the Accord Hybrid's fuel economy (24 mpg city and 32 mpg highway) is not significantly better than that of the four-cylinder gasoline-only Accord--possibly one reason that Honda recently announced that the model is to be discontinued. In its stead, the automaker plans to bring out a clean diesel Accord in 2009.

Like Honda's models, GM's first hybrid is a partial--rather than "full"--hybrid. The Vue Green Line features a basic hybrid technology known as Belt Alternator Starter (BAS), which works by replacing the belt-driven alternator and starter motor with an electric motor that serves as a generator and a motor that can be called upon to assist the gasoline engine. Despite its entry-level technology, the Vue Green Line achieves admirable gas mileage for an SUV: it is rated by the EPA at 23 mpg city and 29 mpg highway.

The Civic Hybrid gets a futuristic redesign for the 2007 model year, and its raked front windshield gives a strikingly Prius-like side profile. Like the Accord Hybrid, the Civic Hybrid uses Honda's IMA system, but in the Civic this is mated to a fuel-sipping 1.3-liter engine. The result is a commendable EPA gas mileage rating of 40 mpg city and 45 mpg highway.

With the same Hybrid Synergy Drive (HSD) technology as its egg-shaped little brother, the Camry Hybrid is motivated by a 105kW battery and a 2.4-liter, four-cylinder engine. As well as its sophisticated drive train, the Camry Hybrid comes with a bevy of onboard technology, including a JBL stereo system, Bluetooth hands-free calling, and a voice-activated GPS navigation system.

The GS 450h's powerful V-6 gasoline engine is assisted by a high-output permanent-magnet electric motor, giving the car 339 horsepower and making it the world's first hot-rod hybrid. The GS 450h is an executive pseudo-eco-mobile aimed squarely at high rollers who want to feel good about their environmental footprints while flying along in the left lane of the highway. Fuel economy is not its priority, as evidenced by its EPA rating of 22 mpg city and 25 mpg highway. Nevertheless, the GS 450h does qualify as a super-ultra-low-emissions vehicle (SULEV).

The 2007 Highlander Hybrid features a 3.3-liter V-6 gasoline engine assisted by a 50kW electric motor. The 07 model is available in either two- or four-wheel drive, which get EPA ratings of 28 mpg city and 25 mpg highway, and 27 mpg city and 25 mpg highway, respectively. The Highlander Hybrid is being updated for 2008 model year (pictured) with a bigger 3.5-liter engine, new exterior styling, and interior features including a standalone back-up camera monitor.

The RX 400h features the same 3.3-liter gasoline engine as the Highlander Hybrid, assisted by two electric motors (front and rear). Together, both power trains pump out an exhilarating 268 horsepower. Like the GS 450h, the RX 400h is primarily a luxury car, as evidenced by its 11-speaker audio system, leather-and-wood-trimmed cabin, and voice-activated GPS navigation system. Like the Lexus GS 450h, the RX 400h qualifies as a super-ultra-low-emissions vehicle (SULEV).