In Mexico City, a group of ecologists are wandering from taqueria to taqueria in search of waste cooking oil to fuel an old school bus for an environmental awareness tour from California to Costa Rica.

The bus, which ran on avocado oil during a week-long drive down from the U.S. border, is being used to prove that vehicles can run on recycled fuels that pollute less than gasoline as it chugs around oil refineries, factories and eateries collecting vegetable oil.

“We’re running low, we have to score some oil today,” said environmentalist Zak Zaidman as crew members called around the greasiest-sounding eateries in the city’s phone directory.

“We have two Japanese restaurants that have lined up a gallon or two and we are trying some taco stands. And we hope to hear back from a restaurant where we had dinner last night.”

The eye-catching 1974 white American bus is loaded with tanks that can carry 350 gallons of oil. Its diesel engine has been modified to run on the more viscous food oil.

Headed for Guatemala, El Salvador, Honduras, Nicaragua and lastly Costa Rica, it left San Francisco on Dec. 1 with 150 gallons of waste oil from local Chinese and taco restaurants.

More here.