A major difference between the BW12 and its predecessor BW8 is that the BW8 had a double oil pump: one on the engine side and one on the propshaft side. This means that the gearbox has oil pressure even if the engine does not run, as long as the wheels are in motion. A DS420 with a BW8 can be started by towing it, which is very rare for an automatic car. This procedure is even described in the Owner's Handbook. The BW12 has a single oil pump only (engine side).