Generally, for this engine and year, a conventional 15W-40 or a synthetic blend 15W-40 oil meeting the API certification of CJ-4 or CI-4 is a suitable choice. If you frequently tow heavy loads or operate in extreme temperatures, a full synthetic 15W-40 might be preferable for better protection and longevity.
Important Considerations:
* Owner's Manual: Always refer to your owner's manual for the manufacturer's specific recommendations. They might specify a particular oil weight or viscosity grade.
* Driving Conditions: If you do a lot of towing or heavy-duty work, a heavier-weight oil might be beneficial. For mostly light-duty driving, a slightly lighter weight oil might suffice.
* Climate: Thicker oils (higher numbers like 40) are better for hot weather, while thinner oils (lower numbers like 10 or 20) are better for cold weather. 15W-40 is a good compromise for a wide range of temperatures.
* Oil Filter: Always use a high-quality oil filter designed for your engine. This is just as important as the oil itself.
In short: While 15W-40 is a good baseline, check your owner's manual and consider your specific usage to choose the best oil for your 2004 Chevy 2500 HD 6.0L. Don't be afraid to consult with a trusted mechanic or parts store professional for additional advice.
