1997 GMC Sonoma Owner's Manual - Page 320

I ShortTriplCityMaintenanceSchedule I 12,000 Miles (20 000 km) 0Change engine oil and filter (or every 3 months, whichever occurs first). An Emission Control Service. 0Check readfront axle fluid level and add fluid as needed. Check constant velocity joints and axle seals for leaking. (See footnote **.) 0Rotate tires. See "Tire Inspection and Rotation" in the Index for proper rotation pattern and additional information. (See footnote +.) 0Lubricate chassis components (or every 3 months, whichever occurs first). (See footnote #.) DATE ACTUAL MILEAGE SERVICED BY: 7-10