IMO, you can get away without an external oil cooler. You still might want to monitor it ( oil temp gauge ). A quality full synthetic oil would be a must. I run a 408 that is about 3/4 filled. No H20 temp problems and oil hasn't gotten over 215 after about 3/4 hour driving around town. The rest of you set up could make a difference though. My oil supplier said that oil temps in the 250 range is not a problem.