1999 GMC Sonoma Owner's Manual - Page 348

yellowblue Long Trip/Highway Scheduled Maintenance j Change engine oil and filter (or every 12 months, whichever occurs first). An Emission Control Service. j Lubricate chassis components (or every 12 months, whichever occurs first). (See footnote #.) j Check rear/front axle fluid level and add fluid as needed. Check constant velocity joints and axle seals for leaking. (See footnote **.) j Rotate tires. See "Tire Inspection and Rotation" in the Index for proper rotation pattern and additional information. (See footnote +.) 97,500 Miles (162 500 km) DATE ACTUAL MILEAGE SERVICED BY: 100,000 Miles (166 000 km) j Inspect spark plug wires. An Emission Control Service. j Replace spark plugs. An Emission Control Service. j If you haven't used your vehicle under severe service conditions listed j DATE ACTUAL MILEAGE SERVICED BY: previously and, therefore, haven't changed your automatic transmission fluid, change both the fluid and filter. Manual transmission fluid doesn't require change. 4.3L V6 Engine Only: Inspect Positive Crankcase Ventilation (PCV) valve. An Emission Control Service. 7-40