Why not use a thermostat sandwhich block behind the oil filter.
The sandwhich block has two ports, in & out to feed an oil cooler.
So it only sends oil to the cooler when the oil gets hot, which is when you need it.
You can also buy oil coolers that have a fan built in.
These also have a thermo switch to turn on the fan when the oil is hot.
regards,
Tony.
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