This is probably going to sound insane but I had this problem acouple of years ago towing through NM. The man at the mom & pop place couldn’t find anything wrong and after a week of searching he ended up checking the air filter just doing a general check and it was pretty bad. He changed the air filter and it took care of the oil problem. I thought it was going to be something major because I had to have a new oil cooler a few weeks prior. The old man said he’d been working on diesels his whole life and never heard of an air filter causing one to go through oil like that. I’ve only had my truck 2 1/2 years and know practically nothing compared to everyone else here but I thought I’d throw it out there for you. I hope it’s something that simple for you as well.