Taken from MBSPY
ASSYST
Active Service System
Engines are equipped with a microcomputer that monitors the aging of the motor oil via data transmitted by sensors and calculates an individualized maintenance plan for the engine: A digital indicator in the cockpit notifies the driver of the number of kilometers remaining before the next maintenance check.
All engines fitted e.g. in the C-class (W203) sports coupé are equipped as standard with the Active Service System ASSYST, which registers the varying operating loads individually and takes these into account for scheduling engine maintenance. On the basis of sensor-derived data such as oil level, oil temperature, coolant temperature, engine speed, road speed and engine load, a micro-computer calculates the actual load on the engine oil and works out a servicing schedule for the engine which reflects this. The central display in the instrument cluster tells the driver how many kilometres can be covered and how many days or weeks remain before the next maintenance service is due. The Active Service System includes an oil level sensor which, as well as warning the driver when the oil level is too low or too high and indicating the amount in litres which needs to be added or drained off, also knows when the driver has topped up with fresh oil and extends the oil change interval accordingly.