In 2008, I knew two guys who had Mercedes diesels that would go around to fast food places and collect their old frying oil. Filter out the french fry crumbs and they were good to go. And yes, the exhaust did smell fast foody.
My little brother did that as well!!! He had a diesel Mercedes and it smelled like french fries when he switched from gas- also, it was so quiet it sounded like the car had been turned off but it was still running.