Biodiesel

biodiesel = el biodiésel

Yes it is safe to mix petroleum diesel and biodiesel. Blends of biodiesel and petroleum diesel are designated "BX." Where "B" states that the fuel mixture is a biodiesel blend and "X" indicates the percentage of biodiesel in the blend. For example, common blends of biodiesel in North America include B2 (2% biodiesel), B5(5%), B20(20%), and B100(100%). B100 is also know as "neat," or pure, biodiesel.

Wikipedia provides an excellent encyclopedia style article on biodiesel fuel. Other websites that offer information about biodiesel fuel are the U.S. Department of Energy's Biodiesel page and the National Biodiesel Board's page.

Yes, you can buy a hybrid that uses biodiesel but they are much harder to come by than hybrids that don't use biodiesel or biodiesel cars that aren't hybrids.