<p>No, Luke didn’t convert the engine on the bus. All diesel engines can run on vegetable oil. What he did was install a mobile filter inside the bus so that raw unfiltered vegetable oil from fast food joints can be poured directly into the bus’ gas tank. Another point to note is that diesel engines, especially those that run on recycled vegetable oil, may not be more environmentally-friendly than petrol-based engines. Depending on the type of diesel engine used, and the kind of filters that come attached, there could actually be more greenhouse gases being emitted.</p>