Hi Lee,If get the engine hot and drain the oil you should'nt need to put any flushing addatives, but if you do not know the history of the van then useing something like Wynn's engine flush (£6 halfords) will help scour out any old crud built up over the years, the quantity of oil depends which engine you have the DE takes 5litres and the DI takes 6.1litres including the new oil filter and the oil should be 5W30 or 10W40 semi synthetic diesel oil
nigel
February 2008