The BMW 525tds Sedan (E34) replaced the BMW 524td Sedan (E34) in September 1991. The diesel engine (M51B25OL) installed in the car represented a new leap forward in the development of BMW diesel technology. Alongside a new engine control system, hydraulic valve-play compensation and a slightly enlarged displacement, the new model featured air-charge cooling for the first time. This gave rise to very sporty driving characteristics with a maximum torque of 260 Nm and an output of 57 hp for each litre of displacement. These characteristics made the BMW 525tds Sedan one of the most powerful vehicles with a diesel engine to roll off a mass-production assembly line.