LOS ANGELES --- California is introducing a new kind of diesel fuel today that's more environmentally friendly. However, the new fuel could cut into trucking company profits, according to the Los Angeles Times. Trucking firms and independent drivers have expressed concerns about the new fuel's cost and availability, the Times reported. This cleaner fuel, called ultra-low sulfur diesel, is almost free of sulfur. Sulfur corrodes an engine's pollution control equipment. The fuel will be rolled out to the rest of the country in six weeks. California gas stations selling diesel must begin selling the new fuel beginning today for all on-road and off-road diesel engines, except locomotives and marine equipment. The rest of the country will follow Oct. 15 for on-road vehicles, but off-road engines won't fall under these rules until 2010. Though the new diesel still contains dangerous pollutants, it represents a major step in the quest for cleaner-burning fuel, air quality regulators told the Times. The new policy lowers sulfur to 15 parts per million from 150 in California and 500 in the rest of the nation. This clears the way for the introduction of new diesel engines with more advanced pollution control equipment. Last week, in fact, Ford said it planned to introduce Super Duty F-Series pickup trucks powered by an ultra-low sulfur diesel engine early next year.