Oil is predominantly heated by rpm's. Consistantly high rpm's will heat up the
oil like it should. A few rapid accelerations on the street aren't enough to get it really hot.
After a while, the
oil temp generally stabilizes at around water temp.
If you have an oil cooler on a street car, your oil will never get hot. Unless you're driving in Phoenix in July.
If you must have an oil cooler on the street, then you really need a thermostat. When fully closed, it will allow about 10% of the oil to flow though the cooler. That allows all of the oil to warm up at the same rate. On a cold day, like 35-40*, the oil still will not warm up; even with duct tape covering the core.
I installed a second external electric oil pump that feeds the cooler only. When it's cold, I leave the pump off, and the oil warms up just like a DD would. On the track I run the pump all the time.
There are two down sides to this set up: First, the electric pump doesn't flow as much volume as the standard oil pump. The oil tends to get about 15-20* hotter than it used to. Not a big deal, since I use Royal Purple.
Second, if the oil starts getting hot, you can't just flip the switch and run the pump. That will inject a big slug of cold oil into the system. And that's a bad thing.