Well, I plugged "What is the ideal engine oil temperature?" into Google, and the first hit that came back has this in it:
"The ideal operating range for engine oil is 180°F through 200°F. While operating within this range, the oil works as a lubricant, coolant, and cleansing agent in the engine. Modern engines generally run with radiator coolant temperatures between 200°F and 220°F with oil temperature ranges between 20°F and 75°F HOTTER. In other words, when the engine is performing flawlessly, the engine oil is already overheating! Oil that exceeds 220°F rapidly loses its ability to lubricate and cool causing accelerated fatigue and premature component failure."
What an Oil Cooler Does
Now, it looks like this page is on the site of a company that sells oil coolers, so I don't know how reliable the information is. I wouldn't stress out over temps going over 220°F if you're using a quality synthetic, for instance. But my point is that you can always Google the question if really want to know. And maybe a search at bobistheoilguy would yield some good answers as well.