I just changed / flushed an unknown coolant from my '85 300D.....and renewed my thermostat......refilled with the high dollar official MB coolant.....

If you haven't access to an MB Service manual.....and if your new Thermostat has an Arrow stamped into it's edge......the Arrow points up......

SB

Forgot to mention......that is probably what long term use of incompatible coolant looks like......why I changed my coolant in the first place.....to avoid something like this....

__________________

Diesels:
'85 300D, "Max, Blue Benz", 155K, 27.0 MPG
'84 190D 2.2, "Eva, Brown Benz", 142K, 40.2 MPG
'77 240D (parts car)
'67 Eicher ES 202 Tractor "Otto" (2cyl, Air Cooled, 30HP)
Gassers:
'94 Ford F-150, "Henry", 170K (300 Six) 17.5 MPG
'85 190E 2.3, 148K....Parts Car
'58 Dodge W300M Powerwagon (Flat Fenders) Less than 10 MPG