Complete Oil Specifications
GM’s 6.6L Duramax Diesel Engine Supplement says engine oils designated API CJ-4 or CK-4 are required for the L5P diesel. Use SAE 15W-40 viscosity grade engine oil; when it is very cold, below -18°C (0°F), use SAE 5W-40 to improve cold starting. Engine oil capacity is approximately 9.5 L (10.0 qt) with the filter.
When to Change the Oil
The Sierra uses GM’s Engine Oil Life System, which calculates oil life from vehicle use and displays CHANGE ENGINE OIL SOON when it’s time to change the oil and filter. The supplement’s maintenance schedule says to check the oil life percentage every 12 000 km (7,500 mi), and:
- When CHANGE ENGINE OIL SOON displays: change the oil and filter within the next 1 000 km (600 mi).
- At least once a year: change the oil and filter and reset the oil life system, even if the system hasn’t asked for it.
- After an accidental reset: service the vehicle within 5 000 km (3,000 mi) since the last service.
- PTO or extended idle use: one hour of use is treated as the same as 53 km (33 mi) of driving.
What We Couldn’t Confirm
- Capacity without the filter, OEM oil filter part number and drain plug torque. None appear in the supplement.
FAQs
What oil does a 2023 GMC Sierra 2500HD 6.6L Duramax take? SAE 15W-40 engine oil designated API CJ-4 or CK-4, or SAE 5W-40 below -18°C (0°F).
How much oil does it hold? 9.5 L (10.0 qt) with the filter. GM describes this as approximate.
How often should I change the oil? When the Engine Oil Life System calls for it, and at least once a year.