Experience
These are probably the most durable diesels engines available. Keeping them fluid leak free is the main challenge. What does that mean? Well for starters, you'll want to keep the oil changed more frequently if you get one that is already leak free or has no active oil leak(s). I would suggest every 3,000- 4,000 miles. If you get one that is already leaking, I would suggest you start the fluid leak remediation journey by replacing all 6 injectors. Not only that, while you are that deep in the engine, change every hose, seal, gasket, and oil cooler. If you still have a oil leak after that ,you have a cracked engine.