SAN FRANCISCO – City-owned vehicles in San Francisco, including fire engines, buses, and even a mobile zoo, will use biodiesel fuel now that an executive directive has been issued by Mayor Gavin Newsom. The order calls on city departments that currently use diesel fuel in vehicles and equipment to switch to biodiesel fuel in 100 percent of their fleets by the end of 2007. The San Francisco Fire Department announced a six-month pilot program to test the use of biodiesel fuel on nine engines, trucks, and an ambulance. Other city departments that also have tested and use biodiesel in vehicles include San Francisco International Airport, Public Works and Muni, as well as San Francisco Zoo in its van service that brings animals to children around town.