the problem with using veggie is that it is quite a bit thicker than diesel and if you are using it in some engines that is not a problem as they have pumps that are strong enough to stand the extra load but others (lucas pump) are weaker and will break recently i was told a weakness in a lot of common rail systems is the low pressure pump which if it fails feeds debris into the high pressure pump also the temperature of the oil has an effect on vicosity hence the prevalence of two tank systems (start on diesel till the veggie has warmed up then switch over) so your local ambient temperature will affect starting adding a solvant helps but you have to be carefull what you use as if you use kerosene this is not road legal and the tax man can hound you it is probably a good idea to add a cetane improver to your mix (i use miller dieselpower plus)
for more info on modified veggie go to
Bio-Power Index page and info on twin tank systems try
DieselVeg Home - Diesel to Vegetable Oil engine conversions also next months issue of car mechanics is going to run another article on veggie ps the current state of play on mine is still running fine but it isnt being used much at the moment only for local journeys
best wishes glenn