GMC SIERRA 2020 Owner's Manual page 448

Service and Maintenance 447
Maintenance Schedule
Additional Required
Services - Severe
Rotate tires and perform Required Services.
Check engine oil level and oil life percentage.
Change engine oil and filter, if needed. Check
engine air filter life percentage and status.
Change engine air filter, if needed.
Replace passenger compartment air filter. (1)
If the vehicle is not equipped with the engine air
filter life system, replace engine air cleaner
filter. (2)
Inspect evaporative control system. (3)
Replace spark plugs. Inspect spark plug wires.
(Except 2.7L L4 Turbo Engine)
Replace spark plugs. Inspect spark plug wires.
(2.7L L4 Turbo Engine Only)
Change automatic transmission fluid and filter.
For GVW under 3 900 kg (8,600 lb), change
transfer case fluid, if equipped with 4WD. (4)
For GVW over 3 900 kg (8,600 lb), change
transfer case fluid, if equipped with 4WD. (4)
Drain and fill engine cooling system. (5)
Visually inspect accessory drive belts. (6)
Replace brake fluid. (7)
Replace windshield wiper blades. (8)
Replace hood gas struts and tailgate
dampener. (9)
Replace air conditioning desiccant. (10)