Any problems with this? SUV is out of warranty and I thought that the Delvac 5W-40 would be a good way to try and prevent sludge build up in this engine which is know to get dirty. Will using a deisel oil or 5W40 oil hurt the engine?
With a jump of only one weight grade, I very much doubt it. If he was jumping to a 50 or 60 weight, I would worry about that, but not a 40. If it were me, I'd just listen very carefully for any increased valvetrain noise. If the engine was quieter overall, I would expect it to be fine.