GMC Yukon XL 2015 Owner's Manual page 400

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.
Inspect evaporative control system. (1)
Replace engine air cleaner filter. (2)
Change automatic transmission fluid. Change
filter if serviceable.
Change transfer case fluid, if equipped with
4WD. (3)
Replace spark plugs. Inspect spark plug wires.
Drain and fill engine cooling system. (4)
Visually inspect accessory drive belts. (5)
Replace brake fluid. (6)