Gone are the days when every driver used a dipstick to check the oil level before driving. Now this function is assigned to the oil level sensor. The dipstick, however, remained, but it is used mainly when refueling the engine with oil. The oil level sensor is also used in the transmission.

1. 5 (E39)
2. 5 Saloon (E39)
3. 7 (E38)
4. 7 Saloon (E38)
5. 5 Touring (E39)
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The usage of the engine oil level sensor

Oil level sensors of several types are installed on modern cars: float, thermal, ultrasonic, and capacitive.

The float-type oil level sensor is the simplest in design. The float moves along a vertical guide (tube). There is a magnet inside the float, and inside the tube, there is a magnetically controlled contact (reed switch). The contact is activated when the magnet approaches, which corresponds to the minimum oil level in the engine.

The most widespread on cars is the thermal oil level sensor. The sensitive element of the TRUCKTEC AUTOMOTIVE brand Sensor, engine oil level is a wire that briefly heats up to a temperature higher than the oil temperature. After disconnecting the power, the wire is cooled down to the oil temperature. The oil level is calculated from the time it takes to cool the sensing element (the more oil in the crankcase, the faster the wire cools).