HAGA, Japan - Diesel engines deliver great mileage but emit polluting gases. Fuel cell vehicles are zero-emission but look bulky. Honda's latest innovations counter the stereotypes. The latest fuel cell vehicle from the Japanese automaker, planned for limited marketing in Japan and the U.S. in 2008, has a slick, streamlined, close-to-the-ground look. Honda Motor Co.'s next-generation diesel engine delivers as clean a drive as a low-emission gas engine of comparable size. Honda's showcased its latest developments in clean driving to reporters recently at its research facility north of Tokyo. In a test drive, the FCX Concept fuel cell vehicle zipped quietly and effortlessly on a course at about 100 miles per hour. Honda declined to give a price for the vehicle. Like other fuel cell vehicles, the new model runs on the power produced when oxygen in the air combines with hydrogen that's stored in the fuel tank — producing only harmless water vapor. Old-style fuel cell stacks, the main part of the fuel cell vehicle, are usually placed under the floor of a car, making for thick floors and a box-like look. Honda's new fuel cell stack is 20 percent smaller than the one it developed in 2003, and can sit in between the driver and passenger's seats in the front, where the stick shift lies in a regular car. It weighs 67 kilograms (148 pounds), or about two-thirds of the 96-kilogram (213-pound) 2003 version, and far lighter than the one released in 1999, which weighed 202 kilograms (445 pounds). But it produces more power. Another innovation in the works at Honda is the next-generation diesel car — planned for the U.S. market within three years. Diesels are growing in popularity in Europe and some other parts of the world because of their fuel efficiency, and automakers have been working on technology to reduce diesel emissions as nations toughen environmental standards. Honda said its new engine meets standards applied in the U.S. state of California, the world's most stringent. The key to Honda's diesel innovation is the catalytic converter attached to the engine. Honda used an ingenious way to generate ammonia — a substance that can turn harmful nitrogen oxide into harmless nitrogen. Diesel engine systems already use ammonia to reduce nitrogen oxide emissions. But Honda's system is self-sustaining and more efficient than others, company officials said. Honda President Takeo Fukui said Honda is serious about fighting global warming and reducing pollution. "Honda believes in the importance of keeping a creative spirit and upholding high ideals," he told reporters.