1999 GMC Sonoma Owner's Manual - Page 331

yellowblue Short Trip/City Scheduled Maintenance under one or more of these conditions: - In heavy city traffic where the outside temperature regularly reaches 90_F (32_C) or higher. - In hilly or mountainous terrain. - When doing frequent trailer towing. - Uses such as found in taxi, police or delivery service. If you do not use your vehicle under any of these conditions, change the fluid and filter every 50,000 miles (83 000 km). j Inspect air cleaner filter if you are driving in dusty conditions. Replace filter if necessary. An Emission Control Service. (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 Change automatic transmission fluid and filter if the vehicle is mainly driven 78,000 Miles (130 000 km) j Change engine oil and filter (or every 3 months, whichever occurs first). An Emission Control Service. j Lubricate chassis components (or every 3 months, whichever occurs first). (See footnote #.) (Continued) DATE ACTUAL MILEAGE SERVICED BY: 7-23