Just five years ago, finding out which cars and trucks were less harmful to the environment was a difficult task. Car buyers had the annual compilation of fuel-economy figures by the U.S. Environmental Protection Agency (EPA) and little else. Today, however, it's a much easier chore for the consumer to consider how "green" a potential car or truck purchase might be. In fact, there are now two distinct green guides for car buyers, according to a Feb. 25 Knight Ridder Newspapers story by Matt Nauman. One is available free through the EPA's Web site. The other, published recently by the Washington-based nonprofit American Council for an Energy-Efficient Economy, sells for about $9 in bookstores. But much of the useful information in the ACEEE's Green Book: The Environmental Guide to Cars & Trucks/Model Year 2001 can be accessed for free through two Web sites, according to Nauman. In October, the EPA began posting its Green Vehicle Guide on its Web site, www.epa.gov/autoemissions. In January, the agency added fuel-economy numbers for 2001 model-year vehicles to the previously available emissions information, which makes the rankings more complete. The EPA uses the five-star rating system that's already familiar to consumers through the National Highway Traffic Safety Administration's crash-test rankings as well as restaurant and hotel reviews, according to EPA spokeswoman Marion Herz. The EPA divides vehicles into categories, such as compact cars, small pickups, large sport-utilities and a dozen others, and then ranks vehicles from five (best) to zero (worst) stars. The Web site allows users to rank vehicles by category, by star rating or even alphabetically. While it's easy to compare vehicles within a segment using the star system, consumers must take a step back and compare the 0-10 emissions/air pollution score that the site also provides to compare across category lines. That means all five-star vehicles are not equally green, according to Nauman's story. Since each engine and transmission set-up is considered a separate entry by the EPA, its list contains hundreds of vehicles. Consumers must check the fine print to make sure they're checking the rating for the specific vehicle they're considering purchasing. For 2001, 15 vehicles earned five-star ratings from the EPA. They include electric vehicles (the Ford Ranger pickup, the Toyota RAV4 small sport-utility and the tiny Ford Think City car); hybrids (the Toyota Prius and the Honda Insight); and 10 gasoline-powered cars. That list includes five variants of the Honda Civic; three midsize sedans with four-cylinder engines (Toyota Camry, Mazda 626 and Saturn L100/L200); and two sport-utilities with six-cylinder engines (the Pontiac Aztek and the Mercedes-Benz ML320). Within each vehicle-type category, the results can be surprising. The BMW X5 sport-utility with the 3.0-liter, six-cylinder engine and manual transmission that's sold specifically in California and a few other states gets a three-star rating. The same X5 sold elsewhere gets a one-star rating. The two-wheel-drive, manual-transmission, four-cylinder Ford Escape small SUV gets a four-star rating. The four-wheel-drive version slips to three stars, while the ones with six-cylinder engines and automatic transmissions fall to two stars. The 2001 edition marks the fourth year that the council has published its Green Book, although it was known as the Green Guide to Cars & Trucks in 1998 and 1999. Author John DeCicco said his book had helped promote the idea that consumers could buy cars and trucks that were better for the environment. He said only two automakers used the results of the first edition in their advertisements, but now a half-dozen do, including Ford, Toyota and Honda. The big news this year, according to DeCicco, is the relative absence of pure electric vehicles on the Greenest Vehicles list. In fact, 10 of the 13 most-praised vehicles have gasoline-burning engines, including two hybrids with both gasoline engines and electric motors. Last year, that same list included half alternative-fuel vehicles. "It raised my eyebrows," DeCicco said. "I bent over backward to make sure I was not inadvertently leaving an electric off that should be on the list." But, in the end, he determined that only the Toyota RAV4 and Ford Ranger electrics were still available to new users. Surprisingly, the Ranger electric pickup didn't have a high enough Green Score to make the best-of list. Another trend spotted by DeCicco -- a mechanical engineer by training and an automotive researcher by practice before he started writing books -- is the emergence of crossover vehicles. These car-based trucks, such as the Chrysler PT Cruiser and Acura MDX, are "good news for the environment" to the extent that they have better overall fuel economy than some of the traditional "box on a pickup frame" sport-utilities that they're starting to replace. Besides picking the best (greenest) and worst (meanest) vehicles in the 2001 model year, ACEEE's Green Book also includes some greener choices in a broad range of categories, including the Toyota Tacoma small pickup with the 2.4-liter, four-cylinder engine and a manual transmission; the Toyota Highlander mid-size SUV with a 2.4-liter, four-cylinder engine and an automatic; the Chevrolet Venture minivan with the 3.4-liter, six-cylinder and an automatic; and the Ford F-150 full-size pickup with the 4.2-liter, six-cylinder and a manual shifter. Since the Green Book lists all available cars -- as does the EPA site -- consumers can pick the greenest choice no matter what type of vehicle they're buying. The GreenerCars Web site, www.greenercars.com, lists the best picks from each vehicle category in ACEEE's Green Book. At the ForMyWorld site, www.formyworld.com, there's a search button that allows the user to check out specific models of new vehicles and to see how clean or dirty specific vehicles from 1978 to 2001 are. The lists produced by the EPA and the council are similar, but differences occur due to methodology, according to Nauman. The Mercedes-Benz ML320 sport-utility gets five-star ratings from the EPA but only an average rating in the Green Book. Conversely, the Chevy Impala sedan with the 3.4-liter, six-cylinder engine gets the top rating (superior) from the Green Book but only the second-best, four-star rating from the EPA. Both sources put Ford's huge Excursion SUV at the bottom, with the Green Book calling it "inferior" and the government giving it zero stars. With auto sales slowing, one wonders whether fuel economy might become more important to buyers, if only for financial reasons. DeCicco doubts it. During the last economic downturn, he said, average fuel economy fell from 25.4 miles per gallon in 1989 to 24.9 mpg in 1992. But voluntary commitments by Ford and General Motors to improve the fuel efficiency of their trucks and SUVs by improving internal-combustion engine technology, using lighter-weight materials and even installing some hybrid powertrains might have a larger impact in the next few years, he said. As consumer advocate and author Jack Gillis notes in The Ultimate Car Book 2000, several factors besides engine and transmission choices affect fuel economy, including whether a vehicle is tuned properly and whether its tires are at the proper air pressure level. But, he writes, a consumer who decides to buy a car that gets 36 mpg instead of 22 mpg can save more than $300 when driving 15,000 miles annually.