i was led to believe that running oil or bio diesel was cleaner than pump derv,hense why you are advised to ween the car onto it. as the oil or biodiesel cleans the crap out of the fuel lines left by derv.
Even when heated, SVO or WVO is more viscous than diesel. So it puts more stress on all injection components. In PD engines, the injectors are very expensive and would be particularly at risk.
In a two-tank system, if the veggie oil is not properly flushed before shutdown, the nozzles will get clogged. A partially clogged nozzle can direct raw fuel directly at the top of the piston, where it can burn through like a blow torch.
Many of those using WVO or SVO do not properly process the fuel... not clean enough, too much water, etc.
And they think it is okay to stay with the normal oil change interval, but this is wrong. Oil should be changed at least twice as often, and to be even safer then change three times more frequently.
Stuck rings, contaminated engine oil, heavy wear on crank main bearings, destruction of injector nozzles -- there are so many things that can go wrong, that all the fuel savings accumulated over 20k-50k miles can be wiped out and more with just one extra trip to a TDI mechanic.
Do not attempt to burn WVO or SVO in any TDI engine. Get an old beater with an indirect-injection engine -- it will be safer and cheaper.
i thought this was one reason that bio diesel is more environmentally friendly,as theres less crap coming our the other end when its burnt.or have i been reading too many tree hugging site?
Cutting down rain forests, to grow palm trees to make palm oil for fuel, is not a very environmentally sound policy.
you make 2k rpm sound like a long way 
