I just found out the oil cooler on the side of my radiator is for engine oil and it has a thermostat. Mine never seems to get warm. Could there be a problem with it? Where is the thermostat? The car runs at a very consistient temp, is the thermostat important?

1984 MBZ 300TD wagon
1983 MBZ 300D sedan
1984 F-250 IH 6.9L Diesel