Originally Posted by StealthZ

all thermostat plate and by-pass units I've seen are a 90 to 10, allowing 90% of oil to be retained in the engine and 10% to actually flow through the cooler, and when temps reach or exceed the thermostat limits (200) it opens completely to the oil cooler. you don't want it to retain 100% before, as then you would end up having a cold oil surge in your system and would be a shock to the engine. I know MOCAL can do a plate in the temp. rating you want.