I haven't seen anyone come out with an oil cooler for the Z yet except NISMO, but $1200 for an oil cooler (I don't think so!!!). My thought was to use a kit made for a 00' Maxima, since they have the same engine and use the same size filter. Please let me know your thoughts and if it will work?

 

Doesn't the Z already have one? Look in the front cowl. On the far left or right should be a small radiator. I think that is for oil. It is not a steering fluid cooler, as Courtesy Parts is selling a Nismo add on cooler for power steering. I guess it could be a tranny cooler, but I have one on my MT, so I am not sure if that makes sense. Can anyone confirm this? I will look around too.

 

The 350 does have an oil cooler its by the oil filter, the cooler has two coolant hoses coming out of it. These hoses go to the water pipe and the thermostat inlet, so coolant ends up flowing through a ring inside of the oil cooler. The oil passes through the oil cooler on its way in and out of the oil filter, so by the transfer of heat it cools the oil. What I am looking for is an oil cooler that mounts in front of the radiator, and has two hoses going to the oil cooler instead of the coolant hoses. Stillen makes a kit for the Maxima for a reasonable price, but they don't know if my idea will work.

 

but what is the small radiator in the front of the radiator on the right side of it?? as mentioned by our fellow member

 

That is a power steering oil cooler, not sure why NISMO sells one.
If you look in the service manual in the Power Steering section (somewhere in the middle), they show the hose layout with the power steering oil cooler.