While 15W-40 CJ-4 is widely considered a good choice for this engine, older specifications like CH-4 might also be acceptable depending on your specific usage and Ford's recommendations. Modern oils like CK-4 and FA-4 are generally *not* recommended for older Power Strokes due to potential compatibility issues.
Important Considerations:
* Owner's Manual: This is the most authoritative source for your specific truck.
* Oil Quality: Stick with reputable brands like Shell Rotella, Mobil Delvac, Valvoline MaxLife, or Amsoil. Don't skimp on oil quality; it's crucial for the longevity of your 7.3L.
* Oil Filters: Use a high-quality oil filter designed for your engine. Motorcraft (Ford's brand) is a safe bet.
* Usage: If you frequently tow heavy loads or operate in extreme temperatures, you may need to adjust your oil change intervals accordingly.
In short, consult your owner's manual first. Then, choose a high-quality 15W-40 oil meeting the specified API certification (likely CJ-4 or CH-4). Don't hesitate to contact a Ford dealership or a trusted diesel mechanic for further advice if you have any doubts.
