I used to run 15W40 diesel oil in my 235. It gave me no issues, but I’ve since learned that the higher detergent levels in diesel oil are somewhat antagonistic to the ZDDP.
Last couple years, I’ve run VR-1 20W50. It’s not a great deal more expensive, has plenty of ZDDP, without the high detergent levels. Peace of mind, if nothing else.
My truck has always pegged the oil pressure gauge at any rpm above idle and been somewhat low at hot idle (10-15 psi). I haven’t noticed much of any difference in that since switching to the 20w-50.
