rapeseed oil, mix or biodiesel process?

I've just acquired a fair amount of unused rapeseed oil at a fair price,
question is, what's the best way to use this for fueling my 300tdi, and a VW van? to refine it and get involved with biodeisel production, or a simple diesel/rapeseed-oil mix (50/50?)?.

just mix it and wang it in! (not sure about the VW though, guess it depends on the age - don't put it in a VW TDI engine.)

really, cheers
vw tdi a total no no then?
any reason?

I think the injectors in the VW tdi are too tight for the unmodified (gloopy) polymers in SVO, the tolerances ar etoo tight - unlike the old landy engines, where you can pretty much wang anything in!

Ran my 200 on 75+%veg for 8 months (till it became cheaper to fill up with diesel!) with no probs at all, same for my old TD.