Anytime you have more air flow through a cooler, it's going to decrease the outlet temperature of the fluid being cooled. This is also true with coolant radiators that feed coolant-to-oil coolers since those coolers feed off the cold side of the radiator. At highway speeds vs city speeds, the engine's coolant temperature coming out the cold side of the radiator will be cooler too.
It won't be low enough to make much difference ... I'd like to see formal data of how much cooler, especially on a vehicle with an oil cooler. A thicker oil if a few degrees hotter will still provide better viscosity/MOFT protection between moving parts.
PS - wish you could use the quote function. Just hit the
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