Hi,

I been reading on this forum for a few days because I am planning to convert my 1994 250TD to a OM605 Turbo with electonic pump and 722.6. I learned a lot and since I have some experience with WVO I want to share my experiences.

Here in Germany, we have quite a big community of WVO users. I guess for one reason we have very high fuel costs for a very long time now. So I have been using WVO for the last 12 years now. I started with a 1985 200D, a few years later with a 1989 300D, my 1994 250TD and my 1991 200D Automatic.

I used many different sorts of WVO, the best fuel which I still use today, is a vegetable sunflower oil (not fat), that was used for frying, and is filtered through a centrifuge. This oil is useable at every temperature, even in the winter at -20° Celcius (with minimal difficulties)

In the beginning, i made quite a lot of modifications to the engine, which over the years proved senseless. First thing I installed with a lot of effort, was a two-tank fuel system which turned out to be totally senseless for the prechamber engines with inline injection pumps (Not for the 220D with lucas pump). Later I installed a big fuel/water heat exchanger to heat the thick WVO up and make it liquid. Turned out, the injection pump is the best preheating device. I also installed electical pumps at the fuel tank to force the fuel to the engine. I learned that the lift pump is strong enough for vegetable oils as long as they are liquid (everything you can put in the fuel tank through a funnel). For greases you need these pumps.

So, for waste wegetable oils, I do these modifications to the w124s:

- cut out the fuel filter in the fuel tank

- install a large fuel line from the tank to the engine compartment. For a 200D, 10mm inner diameter will be enough, for all other engines i use 12mm. I use normal polyamide pipes, as they are used for compressed air in trucks (2€/m). Using smaller diameters causes "undersugaring" of the engine at low temperatures when the engine is cold. The fuel tank will heat up when the engine heats it over the flowing back fuel, but when the fues tank is full, it can take up to 100km. I use a fuel pressure gauge to measure the fuel pressure at the intake of the inline pump, optimum is +0,6 bar. After a cold start on a winter morning with -10°C under full load, the pressure should at least stay over 0,1 bar. The engine begins stuttering at -0,5 bar (yes, the inline injection pump can suck quite good, but not when there is air in the line).

- In the engine compartment, I send the fuel from the big line from the tank into a 8mm ID rubber hose, as it is used originally. It is flowing through a normal inline prefilter through the original fuel-water heat exchanger (the thermostat is thrown out) into the lift pump. From there as it is built by the engineers originally. Since 4-Valve engines have the thermostat inside the heat-exchanger housing and it tends to get leaky with vegetable oil, I normally dont use this preheater. The original prefilter can be used and is practical to clean on the road, but I also get better results using a standard inline-prefilter. On the 4V-engines, all the O-Rings on the fuel lines should be replaced, viton is not necessary (maybe after 10 years of biodiesel).

- I set the injection timing 3 degrees earlier, to the 12° after OT mark (on non-turbo-engines). Injection nozzles are replaced and set to 135 bar (worked best for me). To compensate the higher pressure, a half turn on the fuel quantity screw is needed (never really understood why that happens since its a hydraulic system, I guess the the high-pressure fuel lines are expanding under higher pressure)

- a catalysator helps to minimize the exhaust smell

With these modifications I got my cars running for the last 12 years and 360.000km. I always use 100% WVO, No Diesel or Petrol fuel in the tank, even in the winter. Under 0°c I need to preglow for 30 seconds to get the engine started without using the starter for more than 3 seconds. The 4V-engines start a log better than the 2V. Even at hot summer temperatures, at a cold start the engine is always running shaky blowing blue smoke out of the exhaust.

I never had problems with fuel in the engine oil, at least it has never smelled like vegetable oil. Oil level stays constant from oil change to oil change (10000km), maybe the burnt oil is filled up with fuel. Also I had never problems with burning residuals in the cylinders. As leaking cylinder head gaskets are a normal problem on the OM60x (except the turbo ones with the metal gasket) i have seen all my engines from inside, also the prechambers which I pulled, never had any more residuals than engines driven on diesel. Power is also no issue, only the top speed is only reached after some driving. While my 300D reaches top speed of 200km/h on Diesel immediately, on WVO is sticks at 190, after 15 minutes of fast driving it is no problem to reach 200km/h for the rest of the day. Last year I drove 800km from munich to hamburg, the engine reached GPS 207 in the flat land after one hour of almost constant over-200-driving.

On my second 200D I tried waste motor oil one winter long. I work in a Mercedes-Benz truck workshop, I put the 40l of old engine oil from the Actros directly into my fuel tank. Engine modifications as described above. At first I had no problems. Engine started like it was diesel, just smelled a bit. But three mornings later the good times were gone. From that day on, I had to use the starter for at least 20 seconds to get the engine running. I never solved this problem, I guess the engine lost compression. I did the head gasket some time later, everything looked normal. I put some Petrol on the pistons, but it did not run very fast into the oil pan. Maybe the injection pump is damaged, too. Prechambers were filled completely with coal, i cleaned them, but the problem stayed. Injectors were replaced, glow plugs of course. Liftpump is OK, too. The problem stayed. Even when I use WVO. I dont drive the car any more, just used it in the winters cause it is in quite bad shape. Otherwise I would have tried changing the pump.

I hope my experiences are of some interest.