I just hauled a load with my truck last weekend. It was a 35' dual tandem gooseneck weighing 25k gross (truck and trailer), and I was seeing coolant temps between 190 and 225 and oil temps from 230 to 260. Most of the time it was around 200 and 240, but the longer grades (keep in mind this is relatively flat Texas) would push them up to the high end. I'm considering a new fan clutch and auxiliary oil cooler. Don't haul much, but when I do, I don't want to worry about cooking a piston or bearing. On the really long grades that got the oil temps up there, I was seeing as low as 26 psi oil pressure at 2k rpm. That can't be good for the motor.