Dustbuster

Has anyone noticed their oil temps increasing as the car ages? In the last 12 years mine has crept up from an average oil temp of ~220 to an average temp of about ~240 this year. The car has about 120,000 miles. It doesn't seem to matter if it's 60 degrees outside or 90, the oil temp is about the same. Perhaps the oil cooler isn't working as well, though I'm not entirely sure how to determine oil cooler efficiency? I have run either Mobile 1 5W-40 or 0W-40 for it's life, so I don't presume it's any change in the oil formulation.
Any thoughts?