WASHINGTON - Honda recently won the "Greenest Automaker" title from the Union of Concerned Scientists (UCS) for the fifth consecutive time, narrowly beating Toyota and Hyundai, which tied for second.

"It was a photo finish, but Honda is still the champ," said Jim Kliesch, a senior engineer in UCS's Clean Vehicles Program and the author of the rankings report.

UCS's "Automaker Rankings" analysis ranks automakers based on average per-mile smog pollution and global warming emissions of the entire fleet of vehicles sold. The science organization scores each of the top eight automakers against the industry average of all eight combined. The methodology weighs smog and global warming scores equally to determine each automaker's overall score. With the industry average assigned a score of 100, automakers' scores reflect how far above or below average an automaker pollutes, UCS said. Lower scores are better; higher scores are worse.

"Honda is now five for five, though to retain its title in our next analysis, it will need stronger sales of efficient hybrids and better environmental performance from its conventional vehicles," said Kliesch. "Toyota also will need to make fleetwide improvements to stay in contention. Without its successful Prius hybrid, the company would have placed fourth this year instead of second." As to these companies' newest competition, said Kliesch, "Hyundai, the new kid on the eco-friendly block, could be a real spoiler in the coming years."

Honda finished with an overall score of 86, reflecting a fleet 14 percent cleaner than that of the top eight manufacturers combined. Toyota and Hyundai each finished with 87. Volkswagen came in fourth place (90), followed by Nissan (93), Ford (108), General Motors (109) and Chrysler (113). The analysis is based on model year 2008 data, the latest available.