It says that Thunderhill elevation is 293ft. That is excellent as high altitude will create more issues than ambient temperature.
I had issues with oil temperature here in Colorado, but High Plains Raceway here is between 4,900-5,200ft, which puts a lot of strain on cooling system.
That being said, I would still do some retrofit. I am doing oil cooler now, stock from N55. But, you really do not need that IMO in CA unless going to some high altitude tracks. What I would do is go this route:
https://www.ebay.com/itm/07-13-BMW-N...8AAOSwzDxfpKog
That is much cheaper than dedicated oil cooler, as with oil cooler there are numerous other stuff that needs to be changed. This heat exchanger is pretty simple, effective, and in normal driving might save you some fuel as it will accelerate oil warm up. There is one more coolant hose you need to add if manual, not sure about automatic transmissions. But, search on Google, there are threads by people who did it.
I would go this route before you go bigger radiator.
Also, code your mpg gauge to oil temperature gauge so you know your oil temperature.