I run my 240D on WVO in a two tank system. I'm not sure the risk of a single tank system is worth killing my engine, although I have spent a fair amount of time figuring out how I could do it and have it be realiable.

You can run WVO in an unheated system. The deal with VO is that it won't burn completely if it's not hot enough. VO is too viscous to burn properly at most ambient temps. When VO is too thick it won't spray out of the injector properly. Which can cause problems, namely incomplete burning of the VO. What happens when WVO and it doesn't burn completely, among other things, it gums up the piston rings, so they don't seal to the cylinder wall like it should. Which eventually will begin to allow the unburned VO into the motor oil. When motor and veggie oil mix the motor oil in the engine will polymerize, turns to sticky goo. I've seen it happen. When your oil turns to goo your engine gets no lurbication, and thus it will seize in short order. The trick to all this is that there is a threshold for how much VO can be in the motor oil before it polyermizes. The motor oil will stay oily until a certain volume of VO gets into the motor oil. At that point the oil imediatly turns to goo. If you change your oil often you can avoid this.

The worst part about any single tank conversion is you are starting the engine on cold VO, which is the worst thing you can do. You can do some pretty simple modifications to solve this issue. If you install injector line heaters that you can turn on before you start the car. And if you created a heated loop with that the injection pump and an auxillary fuel pump that you could also turn on before the car is started you could raise the temp of the VO before the car starts and alleviate the cold VO starts.

__________________