Cold Oil into Hot Engine from Oil Cooler

[Modena]

I am using an "ImprovedRacing" thermostat that avoids this, here is an excerpt of their explanaion of how the unit operates;

https://www.improvedracing.com/

The way it works is there is a bypass valve in the center, that connects the two sides together. This valve is normally open when the oil is cold. Because there is more resistance for the oil to flow through the cooler and lines, over 90% of the oil simply flows through this bypass and goes back to the engine.

We do it this way instead of cutting flow off to the cooler completely because:
1. It prevents the system from being "shocked" by a sudden flow of cold oil in the cooler
2. It prevents air bubbles from accumulating in the lines or cooler
3. It allows oil in the cooler to be drained more easily.

When the oil reaches operating temperature, the valve closes the bypass, and all of the oil is now forced through the cooler.

[AL427SBF]

Originally Posted by Modena

...
1. It prevents the system from being "shocked" by a sudden flow of cold oil in the cooler ...

Is this correct? I think they mean prevents the system from being "shocked" by a sudden flow of cold oil in the engine.

[bobcowan]

Originally Posted by Gav

Unless you are planning to drive your car in sub zero temps your oil won't get cold enough in the cooler to cause issues.
Here in Oz we don't get the extremes that they do elsewhere.

A cobra looks a bit funny IMHO without an oil cooler up front though!

Not true. Doesn't need to be sub-zero to create a problem. It's common for me to leave the house in the morning with temps in the 40's. On a highway cruise, there's a lot of air flow and not many rpm's. Even with the thermostat "closed", the oil would not get to operating temp. Tried covering with duct tape, plastic, and cardboard. Those things helped, but the oil never really got up to temp.

Originally Posted by AL427SBF

Is this correct? I think they mean prevents the system from being "shocked" by a sudden flow of cold oil in the engine.

Both, actually.

If the oil is cold, and you get on the throttle a bit, the oil pressure rapidly rises with rpm's. If the oil is too cold and too thick (a lot of people use 20W-50 oil), you can actually burst the oil cooler from the pressure spike.

If the oil in the cooler and lines are cold and the thermostat suddenly opens on a warm engine, then a thick and cold slug of oil will hit the bearings, rotating assembly, and valve train. If you're at speed, bad things will happen.

Using something like a 5W-30 or 0W-30 oil will help prevent all those problems.