Well, I got my gaskets in so there was no point sitting around the house any longer today. Hot and sunny outside, so I went for another oil temp test drive. Car's ambient air sensor in the info display was in the 88-92 range throughout the drive. Even Intake air temp (on a scan tool) was ridiculously high, from the hot pavement and heavy traffic. I saw that go as low as 105 on the highway, but it ramped out to the 150's sitting in dead stop traffic backed up at traffic lights. The heavy friday afternoon traffic was not ideal conditions for running the car hard, but on the other hand it gave me the chance to see if temps would run away shutting the car down into traffic after a hard run too.
First off, I ate some lunch at Sonic and left the car idling the whole time (about 15 minutes) to heat-soak everything. Oil temp stabilized around 210-215. Then I went out and drove on the small streets in stoplight traffic. I made my best effort to stay above 4K when it wasn't totally absurd to do so. I'm sure everyone thought I was an idiot cruising around at a deafening 4-6K-ish in 20-30mph steady thick traffic, but whatever
I was only able to get up to about 230-235 doing this, because there were too many stops waiting on stoplight traffic. Of note, however, is that every time I got stopped, the car would bring itself back into the 220-ish range just idling in hot traffic.
Then I went up onto the highway and got a couple of hard WOT runs in (one on the initial onramp, and another shortly thereafter exiting a toll plaza). That got me back to 240-ish cruising on the highway. Then I went ahead and downshifted and kept the revs in the 5-6K range (with occasional peaks above 7K when passing other cars) for a solid 4-5 minutes. This gradually brought the oil up to 260, which is where I decided to call it quits. No sense going over 260 willfully, imho, that's getting into dangerous territory, but it seemed likely that I could have kept on pushing it higher if I just kept doing what I was doing.
At that point I grudgingly forced myself to just flip it into D-mode and drive light the rest of the way back home. D-mode w/ light throttle tends to keep the revs way down, around 1.5-2K-ish when not accelerating. The car quickly brought itself back to about 245-250-ish before I could even exit the highway to U-turn back. By the time I got back to a steady-state speed on the return highway leg, it was back to 240 again. By the time I exited and got home (the furthest point in this trip was perhaps 5 miles from my place), it was back to 230. Given the extreme heat-soak it went through, I went ahead and popped the hood and put a fan in front of the car to idle it back down. It came back to 215 in about 5 minutes and seemed to stabilize about there for a couple more minutes, so then I garaged it and shut it off.
My overall thoughts:
Yes, I need an oil cooler. Days like this (and much worse) will be the norm here during the summer, and on a longer drive, the way I drive, I can easily see myself being oil-temp-limited. That said, the temperature never ran away from me, even when 'stuck in traffic' and such. The oil temp was purely a function of how hard I was abusing the engine at any given time. At any time, if I backed off the revs and the throttle, it brought itself back down in temp accordingly. I'm still not panicked about it, but today definitely moved up my plans to get an oil cooler installed sooner rather than later.
Edit: also, given the variations in oil temp behavior I've seen on different drives in different climate conditions, I think climate differences are playing a bigger role in this than I would have initially guessed.