I know this may be hard to believe, but in the 30 plus years of owning a Mercedes (this includes cars driven by my wife and two children), I have never had a defective transmission, radiator, water pump, caliper, or brake master cylinder. I attribute this "good luck" to religiously changing fluids and filters related to the engine, transmission, cooling system, and brake system. O.K.--I agree that most people do get their oil changed, perhaps not consistently at the desired 5k intervals, but they do change it. According to many customers' thinking, this is the extent of servicing their car. Some people do understand that transmission fluid should be changed; however, beginning in 1997 Mercedes’ electronic transmission was sold as a “lifetime fill." The problem is that if you did not change it frequently, beginning at 50k, the life of the transmission was severely curtailed. After 50k I would recommend changing transmission fluid every 30k miles.
Now to address the two fluids people most commonly neglect to change: first is antifreeze. I wont get too technical with you, but what one needs to remember is that Mercedes antifreeze is good and most other antifreeze products are bad. The correct antifreeze will provide lubrication, a coating of silicates, and keep the coolant from cavitating. Change your antifreeze every two years with Mercedes Benz antifreeze to protect your radiator, water pump, and your mono/heater valve, which is a biggie for many cars. People who own a W140 chassis car can be faced with an expense of about $750 to replace a mono-valve. Typically this valve will fail in the closed position and a lot of W140 owners oft to add a heavy coat to their wardrobe rather than replace this valve! Last but not least, is changing your brake fluid. Brake fluid is hygroscopic, which means it will absorb water over time. When water is in brake fluid it will rust the pistons and the bores, which is what causes calipers to eventually fail. Rust builds up and once the calipers begin leaking, you must replace them. Okay, a final review of your marching orders: change your coolant and brake fluid every 2 years, it will cost about $100 for each service, but it will save you money in the long run...