I have an 04 with 38,000 miles and the ABC fluid has never been changed. Should I flush the system and change it?

Although an entire flush at 38k sounds too much to me, it certainly wouldn't hurt to do so. That way, you would be preventing ABC Pump and Valve issues that many of us have experienced.

In fact, the minimum maintenance would be a rodeo and filter change. I wouldn't dump all the oil yet, without checking the color. Fresh oil is greenish in color. Whereas old, contaminated oil is dark brownish/reddish in color, sometimes with a foul smell.

What is a rodeo change? I understand the filter.

Thanks

Rodeo :

Thanks five337. Good video .

Basically the rodeo mode tests to see if the ABC suspension is working within its limits. It tests for pressure and suspension height, etc. In the process, it moves the fluid around the ABC suspension system and filters it through the ABC filter. That is why a filter change is STRONGLY recommended after a rodeo mode. In fact instead of a flush, Mercedes now recommends a rodeo and a new 3 micron filter that replaces the usual 10 micron filter.

Is the rodeo mode done with special equipment or a special setting in the car?

Rodeo is done through the Star Diagnostic System (SDS) Machine/Computer.

I've got 10 liters of spare oem fluid for your exchange if you decide to do it... At a good price let me know.