I acquired a 2012 5.7 Ram engine with a #5 intake lifter failure. Opon disassembly I found other cam lobes showing signs of wear witch leads me to think it is an oil issue I know from working in a G M shop when they switched from a semi synthetic to a full synthetic oil lifter issues seam to dissipate. Plus I think today's bulk oils are crap. And as far as maintenance most people do not adhere to regular schedule, if they were on a 3000 mile interval they would do it at 6000, 5k would be 10k, 7500 would be 15k.
