Photos: Dealers hold the keys to biodiesel cars

Late-model Volkswagen Jetta TDIs are among the most sought-after vehicles that easily accept biodiesel, in which soy oil is a key ingredient. However, drivers looking to convert their cars to run on cheaper (or free) french fry grease and veggie oil prefer the more compatible pre-1996 Volkswagens or pre-2004 Mercedes.

Photo by Elsa Wenzel/CNET Networks