Optimum oil temperature

[Tony H]

The topic of oil coolers has me wondering what the Optimum oil temperature is given the ability to regulate it. Too cool=more friction and moisture, too hot=decreased oil and engine life.

[Frank Reiner]

As an example, early M110 oil thermostats opened at 100C (212F).
Later versions opened at 110C (230F), to ensure boil-off of water condensation & other junk.

[rwd4evr]

Originally Posted by Frank Reiner

As an example, early M110 oil thermostats opened at 100C (212F).

Later versions opened at 110C (230F), to ensure boil-off of water condensation & other junk.

That's a useless oil cooler at that point. Water evaporates out of suspension in oil at like 160-170f. I was de-watering motor oil to make diesel for years. Never went or needed to go higher than 180°. It would gather on the lid of the barrel I had sitting at an angle and run off until it was gone. it would start getting stinky and easily flammable any higher too. I would want my oil at 180° in the car if I had my way.

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[Tony H]

My oil cooler bypass valve situation has opened a mental can of worms about something I never gave any thought to. The only car I ever owned with a oil cooler were my VW's/914. My XKE did not have a oil cooler and it was intended to be driven at sustained high speeds. A lot of MB's don't have oil coolers.

[rwd4evr]

Yeah, the vast majority of r107 don't have them. I've been beating the **** out of my iron block forever essentially without one. It's connected but there's no valve in it so a very small amount of oil actually flows through it. For a street car I wouldn't be super concerned. If you have a thermostat on it I'd just have it closed below like 150° then always flowing. The engine will keep warm. If it's winter you can always block the cooler fins.

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[Tony H]

Yea mine had one originally but it was designed to run at full throttle on the Autobahn. For normal street driving at 2500rpm it's much less stressful. I may just bypass it. If I am really concerned I could install a oil temp gauge in a inconspicuous location. I thought of mounting the sensor in the oil drain plug by drilling and tapping it. With 7-8 qts of oil in the giant, finned oil pan it should not get too hot.

[Sugar Bear]

I had to eliminate one on a Euro 380SEL to fit in a larger US radiator. The US 380SEL of that year didn't have a cooler, worked well long term without problems.