are you getting temp reading from a truck gauge or a diagnostic instrument? in other words verified oil is actually 250 degrees?

If the malfunction lite is not coming on you are good these trucks run much hotter then the old school macks also make sure your oil is not diluited with fuel or water this will thin the oil making it hotter .

have you checked to see if your oil pressure sensor is defective? simple things first

I have had these problem's in the past. If it really is that hot. What is the EGT temp. also what is the engine water temp. Cross all these numbers and find one that is heating up first or last. if your EGT temp, is relly high the piston oil cooling will heat the oil. might be a turbo problem plugged sticky or cracked. but check the gauges first. Make sure it is not a faulty reading. Find a temp gun and check the temp of the oil filter's. What engine are we talking about? Does it heat up at idle or pulling or what makes it heat up. You could even have bad bearings. Take a oil sample and have it tested. How many hours on engine?