strange day - yesterday- while driving on the interstate in my 1998 C-230 I noticed my LOW COOLANT & LOW WINDSHIELD FLUID light would intermittently come on simultaneously. The fact the two lights came on as they did had me thinking an electrical issue.
Being safe I pull over and check the coolant, I see floating on the top of the overflow tank small droplets of a darkish liquid, is it motor oil or transmission fluid? I sak myself. When I wipe the inside of the overflow tank a brownish sludge stains my finger.
This morning I suck out the coolant from my overflow tank, (I recently did a coolant change of 50/50 MB brand coolant and distilled water plue REDLINE waterwetter.) the extracted coolant showed no oil deposites and a lite sludge on the insdie of the overflow tank may have been radiator scale.
Poured in new fluid in the overflow tank this morning and no oil has appeared in the coolant as of this evening.
Any ideas?

The fix for the LOW COOLANT & LOW WASHER FLUID lights coming on intermittently and simultaneously is a new windshield washer reservoir level sensor, easy do it yuorself repair, no tools needed, and part is around thirty dollars.

If an inspection from under the car at the head gasket shows no oil leaking, and there is a tiny amount of oil in the coolant overflow tank it is NO big deal.