Why aftermarket oil-to-air engine oil coolers are a very, very BAD idea!

Apr 27, 2022
I've spent the last three hours removing an aftermarket engine oil cooler on an 80-series Land Cruiser.
I might understand the need for an aftermarket transmission cooler. For some particular scenarios, it makes perfect sense.
But why on Earth would some aftermarket manufacturer want you and me to install an oil-to-air engine oil cooler is beyond reasoning.

Engines already have built-in oil coolers through the engine's liquid-based cooling system. It's a double-circuit heat exchanger between oil and coolant. Even if some folks don't see it, it's there.
Now, maybe... just maybe, the vehicle engineering miscalculated, and the vehicle ended up having a sub-par oil-coolant heat exchange.
You don't add an ambient oil-to-air heat exchange device in front of the grill. It's wrong on so many levels.
Imagine cruising on the highway at 80mph during winter, for example.

1. You'll throw the oil out of the temperature/viscosity operating specs
2. Oil flow will be reduced because of the increased viscosity
3. Filtration volume will be reduced in the case of oil filter plate coolers because of the restricted oil flow
4. Unless you drain all the oil in the system, including the radiator and pipes (which I highly doubt most people do), you'll dump ~ 1.2 liters of waste oil into the new clean oil, reducing its performance
5. You'll induce additional failure scenarios: hose rubbing, leaks, joint leaks, radiator leaks, mount corrosion, and front impacts.
6. You'll add additional complexity to the vehicle, making it more difficult to service - in this particular case, the starter motor could not be taken out without disassembling the oil cooler plate.

If I need my engine oil to be cooler, maybe I should check if my cooling system is operating correctly. A higher surface coolant radiator is first required if it's a racing rig.
Then, if the oil temps are still high, maybe an additional oil-to-coolant engine oil cooler is needed, and NOT in series with the oil filter.

Sorry if my post is a bit harsh; English is not my native language.

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