OR......you can install a real oil cooler on passenger side of the radiator. During hot weather simply remove the plastic shroud in the grill allowing direct air flow over the oil cooler. In cool/cold weather install the plastic shroud keeping direct airflow off the cooler.
Mine hasn't been tested in our desert heat yet but with shroud in place my oil temps have stayed the same in our cooler weather Phx is now experiencing. Sorry, but yes low 40'sF is cold around here! What I did notice was instead of taking 6-7 miles of easy driving before my oil temps would begin to come up its about 10-12 miles before temp gauge shows heat.
Remember, the factory exchanger is just that....an exchanger. If you run oil thorough a separate cooler but then back to the exchanger your oil is now exchanging heat with your water. Last I checked water temps are generally higher than you'd want your oil to be at. I believe the factory's intention was to get the oil temps up quickly thus use an exchanger with the coolant.
My sole intention with my setup was to prevent the ECU from killing power when the truck gets too hot. During our summers it only takes a little stop and go traffic and a couple WOT starts to get the ECU to take over and kill HP. IMHO....oil temp gauge and water temp gauge is all relative however when the ECU kills power you know your engine is running on the hot side.