[notfarnow]

There are two ways of using waste vegetable oil as fuel in a diesel engine:

1) BIODIESEL Modify the vegetable oil so that it can be run in your main tank, like regular diesel. You'll often hear it described as B20, B50, B100 etc... that is the ration of biodiesel/regular diesel. B100 is 100% biodiesel. Biodiesel can be run as regular diesel with the following exceptions:
-Some older diesels will have a hard time. Biodeiesel will really clean out your tanks & lines, and that will often plug filters, or worse yet damage injectors & injector pumps. Also, biodiesel tends to eat through rubber hoses & seals, causing fuel system problems. Neither of these issues tend to bother newer diesels.
-Biodiesel has a tendency to gel in the cold, often more so than straight vegetable oil. This means you may have to heat your fuel system in colder climates.

2) Straight Vegetable Oil /SVO Modify the car, so that it can run straight vegetable oil as fuel. In order for vegetable oil to burn properly, it needs to be heated to about 70* Celcius (sorry, that obnoxious metric/imperial barrier). This means that you can't (or shouldn't) start a cold diesel engine on vegetable oil, hence the need for 2 tanks. So, you start the car on diesel, and once it's warmed up you switch to vegetable oil. Most people heat the vegetable oil with coolant heat, and use common fuel switching valves from dueal tank trucks. Depending on your climate, you may also want to use a 12V heater to boost the temperature, as long as your alternator can handle the additional 30amp draw.


I've never touched biodiesel, mostly because in my climate I'd have top heat the fuel system anyway, so I figured it would be easier to go whole-hog and do a vegetable oil conversion.

I've been doing it for 5 years now. I've converted my old 87 Jetta (RIP, after 596000 kms), my 96 Jetta , my dad's 1981 Mercedes Benz 300SD, my father-in law's 93 Jetta and my Suzuki Samurai. have logged about 120k miles on vegetable oil, and my father has done about 60k miles since I converted his car 3 years ago.


You'll hear horror stories about clogged injectors, blown injection pumps, etc... but it's almost always someone who either hasn't filtered the oil carefully, or hasn't heated it enough.

I dewater & filter VERY carefully in the garage, to ensure that we don't have problems on the road. We do this with BOTH our cars, so it has to work EVERY DAY. My wife would never tolerate plugged filters on the side of the road.


One thing to keep in mind about Mercedes diesels... they seem to be an exception when it comes to the need to heat the oil. Many people run 50/50 diesel/vegoil in their main tank unheated. That is obviously climate dependant.