Last year’s mushrooming gas prices did more than humble the owners of king-of-the-road SUVs: The gas crunch also has moved interest in eco-friendly hybrids and other alternative-fuel vehicles into the mainstream. The demographics of people buying more fuel-efficient vehicles shifted rapidly from primarily younger, environmentally conscious drivers to include a full spectrum of the population encompassing all ages and income levels. More than 200,000 hybrid cars were sold in the United States in the first 10 months of 2006, double the number sold in all of the previous year.

Travelers curious about alternative-fuel vehicles are beginning to get the opportunity to rent some of the more popular models and experience their capabilities — and limitations — firsthand. Abroad, meanwhile, some drivers are checking out what may be the cars of the future, from the dual-fuel, bioethanol-powered Saab 9-5 to the teensy electric Sakura Maranello 4. There are even places — Vancouver, London, San Francisco and New York — where you can ride in a hybrid taxicab.

In the United States, the most popular — and most widely available — hybrid car is the Toyota Prius, which has a futuristic aerodynamic design. It’s one of a new generation of cars that rely on both a standard gas engine and a battery-powered electric motor that work together to recharge the battery; the gas engine powers a generator, and the electric motor recaptures the kinetic energy of braking.

When fuel demands are low (standing in traffic, for instance), the battery-powered electric motor does the job. As you accelerate, the gas engine kicks in to boost power. This generally means a savings, because you’re not always using gas. If you do a lot of stop-and-go driving or have a lead foot, however, you won’t see as much benefit. Athough the cars specifically designed to be hybrids, the Prius and the Honda Insight, are the most fuel-efficient, the hybrid versions of some traditional models also offer improved gas mileage.

Hybrid cars cost about $3,500 more than the same model fitted with a conventional engine — but a tax credit of $400 to $3,400 depending on the model helps ease the financial sting. The tax credits are computed by how much fuel the car saves over 120,000 miles and by its relative fuel economy for its weight class. That incentive, though, is set to expire in 2009. In the meantime, it’s designed to encourage U.S. automakers that have lagged behind Toyota and Honda to broaden their entries into the hybrid market. Ford’s Escape was the first U.S. hybrid model. This year, GM introduces its hybrid sedan, the Saturn Aura.

Hybrids are by far the most popular of the alternative-fuel vehicles sold in the United States, and although the smaller and lighter-weight versions are the most fuel-conserving, adaptation of the technology to higher horsepower engines means that if you like performance cars, luxury cars or even trucks, you can still “go green.” Among the vehicles available in the hybrid formats are the Lexus RX 400, the Toyota Highlander and Mercury Mariner SUVs, and the Chevy Silverado.

ALTERNATE FUELS
Hybrids are not the only gas-saving vehicles on the road. Diesel-powered cars, long popular in Europe, come in new clean-burning editions, and three models — the Mercedes E-class diesel, the Jeep Liberty diesel and the VW Jetta diesel — are already on the market in the United States.

Diesel aficionados — mainly Europeans — also are promoting what’s known as biodiesel: a fuel made from fats and oils rather than from petrochemicals that can be used equally as well by diesel engines. It can be used in a pure form, called B100 (100 percent biodiesel) or blended into regular diesel fuel in any proportion. It is primarily made from canola oil in Europe, from soybean oil in the United States, and is available at more than 400 U.S. service stations. That makes diesel cars even more appealing to serious “greenies.” Biodiesel is not to be confused with d o-it-yourself alternative diesel fuel that its proponents call “grease,” and which can be (more or less) free. A diesel engine adapter that runs the engine off the primary fuel source until the secondary “grease” source is heated allows these cars to use fuel that’s made at home from discarded commercial-kitchen cooking oil plus some additives; Greasecar.com has all the info.

TAXIS TOO
Saving on fuel is important to taxi drivers, many of whom lost income in recent years as gas prices rose faster than fares. The first hybrid taxi, a Prius, hit the road in Vancouver in 2000; it’s estimated that switching from midsize Ford Crown Victorias, the most common taxicab vehicle, to the Prius could save the average taxi fleet $9,000 a year. Yellow Cab in British Columbia now has 43 hybrids in its fleet.

Two years ago, the New York City Taxi Commission auctioned off discounted taxi medallions for hybrid or alternative-fuel cars, and one winning cab company put 18 Ford Escapes in service by the end of 2005, adding several more in 2006. Drivers are saving an estimated $20 on gas each shift. Some Escapes are also on the road as taxis in San Francisco, and a variety of hybrids and diesels are being used as cabs in London, which actually had a fleet of electric cabs way back in 1897.

According to hybrid taxi drivers, what passengers lack in legroom they gain in novelty — or from feeling virtuously “green.”

RENTING HYBRIDS
With waiting lists for many of the most popular hybrids, rental car companies have yet to make substantial additions of hybrids to their fleets. Several promote their “green” line of rental vehicles, but consumers often are disappointed to find no hybrids on the list. Hertz, for example, restructured its fleet last September to include a “green collection” of vehicles getting at least 28 mpg. Rental-fleet insiders say they notice the shift among corporate renters to larger, “safer” cars around the turn of the century is now reversing itself in response to fuel prices. Because of the relative scarcity of new hybrid cars, the major rental-car companies are reluctant to guarantee them even where they are nominally available; make your request and take your chances. Hertz has had better luck adding the Prius to its fleet in Australia and also is providing some hybrid cars on corporate leasing contracts in the United States.

The largest fleet of alternative-fuel and hybrid vehicles belongs to EV Rental Cars, which has more than 400 cars at a dozen locations throughout the United States, including nine airport locations in California as well as Phoenix, Pittsburgh, and Washington, D.C. The company rents electric cars and cars powered by natural gas as well as hybrids. In another state with a high concentration of the ecology-minded, Oregon, Enterprise Rent-A-Car has added some biodiesel vehicles to its fleet. If you really want to try out a non-polluting “car of the future,” rent a Sakura Maranello from Electriccarhire.com in London. The funny-looking little Italian-built car, which measures less than 9 feet long, can travel up to 62 miles before it’s necessary to recharge. Electric vehicles are becoming popular enough in London, in fact, that an increasing number of parking lots and parking garages are offering free charging ports.

High on Hybrids
Here are 10 popular models of hybrid cars, with their EPA gas mileage. EPA results are derived from testing emissions to estimate the fuel-efficiency ratings. Consumer Reports holds that although EPA ratings for highway mileage for hybrid cars are fairly reliable, the city mileage can be as much as 40 percent lower than the EPA estimates. Rank is in order of models sold in October 2006. Where cars are available in both hybrid and traditional engines, listing refers to hybrid model.

Model / City MPG / Highway MPG

Toyota Prius 60 51
Toyota Camry 43 37
Honda Civic 50 50
Toyota Highlander 32 28
Ford Escape (2wd) 36 31
Lexus RX400 31 27
Honda Accord 30 37
Mercury Mariner 33 29
Honda Insight 61 68