The Mercedes-Benz OM601, OM602, and OM603 engines are part of a highly regarded series of diesel powerplants produced from the 1980s through the 1990s. Known for their reliability, efficiency, and longevity, these engines have powered various Mercedes models for decades. However, like all diesel engines, they require regular maintenance to stay in peak condition. One of the most crucial routine tasks is changing the engine oil and filter at proper intervals. Diesel engines generate more contaminants than gasoline engines, making frequent oil changes essential to prevent excessive wear and maintain performance. This guide provides a step-by-step process for changing the oil and filter in OM601, OM602, and OM603 engines, ensuring they continue running smoothly for years to come.
Specified SAE Viscosity Classes During Continuous Ambient Temperatures
Following the SAE grades
exactly according to the ambient air temperatures would result in frequent engine oil changes.
The temperature ranges for the SAE grades should therefore be regarded as a guideline which
may be exceeded for brief periods.
Oil Capacity in Liters
Torque specifications (Nm)
Special tools
Due to the different sizes, the filter element and the rubber seal ring on the cap should not be exchanged with those on engines 615, 616, and 617.
On vehicles with air oil cooler (turbocharged
engines) the oil need not be drained from the air oil cooler.
NOTE: Change engine oil only with the engine at operating temperature.
Engine Oil and Filter Change
Empty the oil filter before drawing off or draining the engine oil. For this purpose, unscrew the nuts (arrows) and remove the cover.
For this purpose, for reasons of available space, on engine 603 in model 124 (up to January 1986) loosen the rubber gasket or sealing strip on the unit partition as follows and pull slightly in an upward direction.
With a split rubber gasket
Pull off the holding clamp (1).
With a one-piece rubber gasket
Unscrew the screw (arrow).
With a two-piece oil filter cover
(starting February 1986, engine 603 in model
124)
Unscrew the return pipe (276) and remove it. Unscrew the oil filter cover retaining nuts and remove the cover.
Suction engine oil via an oil dipstick tube withthe engine at operating temperature.
If no suction unit is available:
Remove the lower noise encapsulation panel and install it after finishing all maintenance work.
Drain engine oil from the oil pan (arrow).
Note: The oil in the air-oil cooler need not be
drained.
Replace filter element.
Replace the rubber seal ring (1) on the cover.
Check the oil port on matter (arrow). If it is
the oil tube for foreign blocked, remove the
foreign matter by hand. Then blow through the oil port with compressed air; air must noticeably come out of the bottom of the oil tube. If the oil port is not open or if no air comes out, replace the oil filter cap and oil tube.
Tighten nuts to 25 Nm with a torque wrench.
If the oil has been drained from the oil pan, replace the seal ring on the oil drain plug.
Tighten the oil drain plug to 30 or 25 Nm.
Add engine oil.
Run the engine and check for leaks.
Check oil level approx. w minutes after stopping the engine at operating temperature.
To maintain the longevity and reliability of the Mercedes-Benz OM601, OM602, and OM603 diesel engines, regular oil and filter changes are essential. These engines rely on clean, high-quality oil to prevent wear, reduce sludge buildup, and ensure optimal lubrication. By following the correct procedure—draining the old oil, replacing the filter, refilling with the recommended oil, and checking for leaks—owners can extend engine life and maintain efficiency. Proper disposal of used oil and filters is also important for environmental protection. With routine maintenance, these classic Mercedes diesel engines can continue delivering reliable performance for many miles to come.
