Permissable oil temperature

[Paul Kupferberg]

Hello members. My 1964 C with a ‘B’ engine appears to run hot on a warm day (90 degrees). The temp gauge needle is all the way to the right. I measured the oil temp using a deep fry long thermometer, and the actual temp is 200 degrees. My question is this: is this oil temperature within the normal range, in which case I suspect the temp gauge needs calibrating, or is 200 degrees for the oil considered over heating. Thank you as usual for any helpful advice. Paul K

[Doug McDonnell]

200 is fine. With a correctly calibrated sensor/gauge 212 or 100C is center of gauge depending on where you read about the temp. Gauge reading is probably 20 degrees less than sump temp. From my PCA days 220 is hot and 240 is too Da*# Hot unless brief periods. Conservative figures maybe but I like safe.

[David Jones]

Over 250*F for more than about 30 minutes is likely to start oxidizing conventional oil, if it is synthetic you could run at 300*F all day long without oxidation though other parts of the engine would no doubt be suffering if the oil temp got to that level for very long. Remember that the oil at some points in the engine is going to be very much hotter than sump temp and what you are seeing in the sump is the temp of the homogenous mix from heads, valve gear and bearings. Although it is an air-cooled engine the oil is an important intermediate cooling medium and carries a lot of the heat away from the heads which typically run around 325*F so the oil is working very hard when the throttle is being exercised. If I lived in the South or on the West Coast and did long runs in the heat of summer I would be tempted to run a full synthetic.
220*F is not too high an oil temp and anything above 180 should be considered acceptable. Lower than 180 and the high boiling point condensible vapors will stay in solution in the oil and contaminate it so always try and get the engine above 180 before shut off.

[Paul Kupferberg]

David and Doug-thank you very much for very helpful input. I think I will send the temp gauge off to North Hollywood Speedometer and have them calibrate it. This type of help is of immense advantage, as no one in my area has this expertise (West Virginia).

[Doug McDonnell]

When I redid my C I had them install a dual sender and replaced the clock with an oil pressure gauge. North Hollywood sells one that fits perfectly. I have never regretted having the oil pressure gauge. Another way to get the same result is to have your gauge changed to the 904 gauge. http://www.nhspeedometer.com/accessory-gauges-356