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Read our primer articles on High Mileage Oil, Synthetic Oil and Kinematic Viscosity

I find myself seeking the Internet with this question but can't find an answer. A bunch of us on another board who run performance and regular engines (cars) are trying to determine exactly what temps our oil should be. The discussion started with oil coolers and then came to the point of exactly what should the temperature be.

We hear that engine blow by creates moisture in the oil so the oil needs to be hot enough to remove that water. We also hear that oil should be cool enough to keep the engine internals cool as well, but not too cool. We hear that oil breaks down at anywhere between 240 to 270. We just do not have the answer....I found this board and you all seem to know a lot about oil....can anyone answer this one for us.?

Brad
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It's always hard to find an end all be answer to your questions because there is no one size fits all answer.

Understand that when you measure your oil temperature, you are measuring the "average temperature usually in an oil gallery just post oil cooler and oil pump, but without any load on the oil." If you could measure the oil temperature when it is under stress, say in a camshaft/lifter interface, you would find that the spot temperature is much higher than the average temperature, but only for a micro second, then the oil mixes with other lower temperature surrounding oil and averages out.

Oil will oxidize/degrade at room temperature, only the reaction rate is very slow. As the temperature and pressure increases, the reaction rate increases, especially when the average oil temperature gets above about 250°F for any length of time. The longer oil stays hotter the faster it generally degrades.

Chumley
Don't forget as well, what we might think of as "hot" is all relative as well. Given just how hot the combustion chamber can get under a severe load and or high speed, oil temperature, even if at 240F would seem downright "cold" in actually.

I also thought that oil could see an average of 300F in severe climates and/or conditions, hence why we look for a product with a relatively high flash point, right?
If Max bhp is achieved at a water temp of say 90-100c then then the oil will normally be at a slightly higher temp.

To run at a higher water temp will reduce bhp but additional cooling adds weight, so a trade is made between weight and bhp.

Oil will usually run at 90-150c which should not be an issue for synthetic especially ester based, a mineral perhaps should be limited to 130c.

If the oil is run constantly at 110c and above an oil cooler will help maintain viscosity.

To help maintain viscosity at high temps and deal with fuel dilution (thins oil) with carbs or endurance racing then a thicker viscosity oil can be used. This has a downside as a thicker oil runs hotter. An alternative is to use a better quality ester based oil (usually race oils eg Millers, Silkolene, Motul, Redline).
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