I know I'm a little late...but I don't think you'll git a more efficient setup with an air cooled setup than the water cooled oil cooler. Not sure on the temperature of the coolant when it gits pulled from the bottom of the radiator and pumped directly into the oil cooler. Fluids are up to 200 times more dense than a gas as there is more thermal capacity in a fluid than there is in a gas. Someone versed in fluid dynamics may be able to tell you how much more air flow and temperature differential you will need to exceed the capabilities of fluid flow.