I know this is rv.net. But can we please quit comparing apples and oranges?
“My oil is black after 1000miles…” No chit Sherlock. Mine is black after 10 miles. It’s a diesel. Not a danm thing to do with the OPs post.
“My engine doesn’t get worked too hard towing….” No chit Sherlock. OPs engine isn’t an industrial power plant designed for 500 hr OCIs and 90% duty cycle…. Or whatever it is….I expect the same folks will give me overtly literal responses because I had the facts wrong. I’m only speaking order of magnitude.
Best part is OP is now extending his OCIs!! Lol. And engine will probably outlast the truck!