Chevrolet Silverado 2015 Owner's Manual page 494

Service and Maintenance 11-7
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.
Replace passenger compartment air filter. (1)
Replace engine air cleaner filter. (2)
Inspect evaporative control system. (3)
Replace spark plugs. Inspect spark plug wires.
Change automatic transmission fluid and filter.
Severe Service: Change transfer case fluid,
if equipped with 4WD. (4)
Extreme Service: Change transfer case fluid,
if equipped with 4WD. (5)
Drain and fill engine cooling system. (6)
Visually inspect accessory drive belts. (7)
Replace brake fluid. (8)
Replace clutch fluid. (8)