The OM654 engine has been used in numerous Mercedes-Benz cars and vans, and its reliability record is very much dependent on how well it has been maintained. Some owners have reported issues with wear to the valvetrain including camshafts and tappets, while others have passed 150,000-200,000 miles without problems. If you are looking at a used vehicle we would advise looking at a later model as Mercedes-Benz changed the specification of some of the internal parts, and look for a car with a good service history. More frequent oil changes will also help to keep the engine in good health.