Originally Posted by Dustin@Z1

The Middle Eastern market oil cooler kit found on the 370Z from the factory is very similar to what is installed on the older 350Z's (VQ35DE's only). The US spec VQ35HR 350Z's and G35's did not have the factory oil cooler either. The factory style oil cooler kit is different in operation when compared to the oil-to-air style used by the aftermarket oil cooler kits. The factory oil cooler has a sandwich plate that passes oil thru it (it does not exit the sandwich plate at all and passes directly into the oil filter or block). Coolant is passed thru ports in the sandwich plate, sending the coolant around the oil thru passages (similar to coolant passing thru the cylinder block or heads) and extracts the heat that way. There really is not much additional oil added to the engine or that much addional strain or demand placed on the oil pump. I highly doubt that the Middle Eastern market 370Z's would hear any unusual noises like what we experience here.