I have recently been playing with Vegetable oil as a fuel.
I had some experience with my XJ600 Diesel bike. That was fitted with a Yanmar L100 clone, which is a direct injected 400CC single cylinder diesel. That type of engine is not ideal for running on vegetable oil, as fuel gums up the rings when it hits the cold cylinder walls.
The new diesel bike has a Kubota D850 engine. This is an INdirect injected diesel. As a result, diesel is injected into a prechamber, which is nice and hot, the fuel then vapourises and gets sucked into the combustion chamber. This means that the engine is much more tolerant of fuels of different thickness etc, and also means that ring gumming is not so much of a problem.
I also have a Mercedes E300 Turbodiesel as a runabout. This cost me £280 so is ideal for testing various fuel mixtures on it!
I am currently testing waste vegetable oil (or WVO). I prepare this by pouring it into a 100 liter drum, through a 10 and 5 micron filter sock, 5 liters of petrol is also added per 100L of WVO.
Once its in this barrel, it stays there for a week to settle. A tap is then used to drain the bottom 1L or so of rubbish that settles, and the rest is then ready to use.
My initial experiments with both the vehicles have been good. The E300 TD with the OM606 engine runs really well on this mix. It is imperative to ensure there are no air leaks in the fuel system of this engine, ideally before you start putting WVO into it, as they will only get worse on the thicker fuel. Replace all the O rings (including shut off valve o ring) on all the clear pipes before the pump. Also ensure that your strainer (both tank and prefilter) are clear.
Once all done, you have an engine that sounds like this:
and starts pretty well (with one glow plug dead):
The Kubota D850 is pretty much the same, here is a warm start and cold start: