One of the myths about MB's, at least the W124s, is that they are "broken in" at 100K miles. Wrong. They are "
Breaking In" at 100K, meaning that the parts that will break or fail are begining to do so. The car is not really "
Broken In" until 200K miles, when just about everything that will fail has done so.
People get ripped off on repairs because they are not knowledgeable enough, or fearful of, common sense diagnostics. 95% of my car's "problems" have been fluid related -- oil, transmission, PS, coolant and, because they are "fluid" in behavior, rubber belts and bushings.
A person might simply have low trans fluid, but when the tranny flares or whirrs, they run to the dealer thinking there is a true problem, and get hit with an unnecessary repair bill. The steering may be sloppy and they think it is a steering box or major linkage issue, when all they need is a idler arm bushing or a steering damper.
The worse "problems" are those with indirect causes. A leaky PS pump front seal will lubricate a serpentine belt to the point where it starts to slip over the alternator, water pump, PS and A/C pulleys, causing them to spin more slowly, and making an unknowing driver believe he or she is having a slew of mechanical and electrical problems, i.e., low voltage, weak battery (because the alt is not fully charging it) too-hot coolant temp, heavy steering, and weak a/c. They end up spending hundreds, or thousands, of dollars on repairs, when all that was needed was to seal the PS leak ($10 plus 3 hrs time) and blast the pulleys clean with brake parts cleaner. (I actually had this occur.)
Indeed, I am now experiencing this indirect-cause scenario. My coolant is 2 or 3 degrees warmer than normal. After assuring the water level is OK, I thought back to the last thing I did on the car, which could possibly be related to this condition. In February I switched to Mobil 1, to flush the engine. It did a great job of cleaning out all the dirt and gunk, especially that which was sealing the valve cover and other engine components, and allowing oil to seep out pretty freely. Over 5 months, this oil found its way onto the belt and pulleys, as evidenced by the considerable grime I saw on them today. Reverting back to Castrol 20W50, and blasting the pulleys clean and dry again with brake parts cleaner, will resolve that problem. (I will replace the valve cover gasket, but rely on the Castrol sludge to re-seal the less-significant leaks
)
I knew nothing about cars when I got mine, and would panic when things behaved strangely. In time, I overcame my fear of my car, because I recognized how easy M-B made it for do it yourselfers to make repairs (on the W124s).
Some basic knowledge of what the car's components and fluids do;
+ a LOT of common sense;
+ some research at MercedesShop when a problem arises;
= Massive savings on uneccesary repairs.