The brief
Delson, a loyal customer who'd just switched from a BMW 5 Series to this E200, brought the Mercedes in for its Service C maintenance. Service C is a bigger interval than a basic oil change, it's where the longer-life items come due, and on this car that includes the gearbox fluid. The engine oil and filter go on every service. At a Service C the air, cabin and fuel filters come due too, and the brake fluid, which absorbs moisture over time. The automatic transmission fluid does a hard job, lubricating, cooling and hydraulically working the gearbox, and it degrades with heat and miles, so on this schedule the fluid, the transmission filter and the pan gasket are all renewed together. Skip it and shifts get harsh and the box wears faster, so doing it on schedule is what keeps the gearbox happy.
The diagnosis
On the ramp the E200 came up needing the Service C items: oil and filter due, the air, cabin and fuel filters due, the brake fluid due a change, and the transmission fluid, filter and gasket due. The brakes, suspension and the rest of the car checked out fine, nothing failing, just the schedule. So it was the full Service C: oil and filters, brake fluid, transmission fluid with a new filter and gasket, and a full inspection.
The work
The engine oil was drained and refilled with the correct Mercedes-spec oil and a new filter, the air, cabin and fuel filters replaced, and the brake fluid flushed through and replaced. The transmission pan came off, the old fluid drained, the transmission filter and the pan gasket renewed, and the box refilled with the correct Mercedes-spec fluid to the right level at the right temperature, the way it wants it. The brakes were inspected and measured, the suspension and tyres checked, and the service indicator reset. A road test confirmed a clean start, smooth running, crisp shifts, steady braking, and no warning lights.
The outcome
Fresh oil and all the filters, new brake fluid, fresh transmission fluid with a clean filter and gasket, brakes and suspension checked and sound, the service light reset, and a clean health check. Delson got the E200 back with the Service C done properly. The longer intervals are where the expensive parts get protected, so doing the gearbox service and the brake fluid on schedule is what keeps the big repairs away on his new car.