The dealer can install Stillen parts and it doesn't void the Infiniti warranty. That would be the advantage over DIY.

Oil Cooler
 

That stock oil cooler is really what some call a heat exchanger. It is designed more to bring the oil temperature up quickly. It uses engine coolant to do that. It circulates the oil and coolant thru a heat exchanger constantly to keep them both at a relative same temperature. It works because the coolant heats up way faster than the oil. This helps the car by getting the oil temperature up to optimal operating temperature faster.

It can keep the oil cooler but only as cool as the coolant. An external oil to air cooler might lower the oil temperature 20 degrees. Oil works best at a high temperature but not over 240 I think. So like 220 is good but may 200 is better.

the stillen G35 cooler claims a 30-40 degree heat reduction, which would probably be plenty.

Is it applicable to the G37? I sent an email to Stillen requesting info on an oil cooler for the G37 - but haven't heard back yet.

Josh from Stillen said on another post that Stillen will have an oil cooler for our G's early 2009. :)

Limp mode sounds like a MAF sensor or the likes