I go to the petrol station about 2x per year - for the chainsaw.
I run all our vehicles on bio, and have done for about 6yrs or so.
The allowance is up to 2500lts, per annum. Thats for veg or bio.
Technically, veg is a triglyceride, whilst bio is a methylester. Bio is not veg with some sort of thinner in it, despite what the chap down the pub says.
Personally, i would not run a 300tdi on veg, without twin-tanking, and running with heat exchangers. Again, bloke in the pub will say its fine though....
The reason - its a direct injection. The spray pattern from the injectors, firing on cold, viscous veg will be poor. This leads to unburnt fuel, ring gumming, seepage into the sump oil, and emulsification. Not happened to me (as i dont run on veg) but has happened to people i know (as in in real life) on other direct injection engines.
Sure, it will work for a while though.