Some of the PD TDis can be happy to sink a litre every 1000 miles even though working perfectly. They're also supposed to be operated on semi-synthetics only!! Possibly something to do with the injectors being incorporated into the head assembly directly. Pumpe Duse means unit injector and it was a clever system where fuel pressures were never ramped up until immediately before the injection phase.
Why? I don't have any idea. I do know, however, that they injection pressures are insane, circa 3000 bar. I thought my common rail HDi was high at 1300 bar.
My car didn't have a thirst for oil thankfully (despite have an ECU remap), given that the prescribed stuff was a 5w/40 full synthetic low-sulfated-ash formulation=EXPENSIVE.
Still, the problem has been taken away from me now as the car was destroyed in an accident on 24th June. Which is a real shame because I'd planned to keep it another 4 or 5 years. On the bright side, however, I did walk away from a national speed limit road accident with no broken bones and no loss of blood. Lots of bruises/abrasions etc. from airbags, belt tensioners etc. Also the occupants of the other car got away similarly lightly.