What is this round reservoir behind the ABC reservoir?

Thanks

 

I'm pretty sure it's the power steering fluid.

 

The PS fluid reservoir in my W212 is oblong in shape but the cap looks similar. It is on the passenger side.

OP, what side of the engine compartment did you take this pic from? Looks like the driver side based on the freon tubes and possibly air intake. But it doesn't look like my W212.

 

powersteering top
and
radiator overflow bottom?

 

Sorry.. Wrong forum.

This if from my wife's sl500.

Mods... Can you move to the r230 forum please?

 

LOOOOOOL
NO WONDER ALL THAT BE LOOKING STRANGE