Hi I have a 1978 Mercedes 240D. I have been pretty succesful running it on waste vegetable oil. I keep hearing about looping the return so the hot fuel doesn't go back to the tank. I really want to do this on my mercedes but have no idea on how to!!!!. Can anybody please provide me with a diagram, and explain to me how this is done on a 78 mercedes 240D single tank system. It would be greatly appreciated.