2003 GMC Sonoma Owner's Manual - Page 373

Every 100,000 Miles (166 000 km): Spark Plug Wire Inspection. Spark Plug Replacement. 4.3L V6 Engine Only: Positive Crankcase Ventilation (PCV) Valve Inspection. Every 150 000 Miles (240 000 km): Cooling System Service (or every 60 months, whichever occurs first). Engine Accessory Drive Belt Inspection. These intervals only summarize maintenance services. Be sure to follow the complete scheduledmaintenance on the following pages. Every 15,000 Miles (25 000 km): Automatic Transmission Service (severe conditions only). Every 30,000 Miles (50 000 km): Fuel Filter Replacement (4.3L V6 engine only). Engine Air Cleaner Filter Replacement. Front Wheel Bearing Repack (two-wheel drive only) (or at each brake relining, whichever occurs first). Every 50,000 Miles (83 000 km): Automatic Transmission Service (normal conditions). Every 90,000 Miles (150 000 km): Fuel Filter Replacement (2200 L4 engine only). Every 100,000 Miles (166 000 km): Spark Plug Wire Inspection. Spark Plug Replacement. 4.3L V6 Engine Only: Positive Crankcase Ventilation (PCV) Valve Inspection. Every 150,000 Miles (240 000 km): Cooling System Service (or every 60 months, whichever occurs first). Engine Accessory Drive Belt Inspection. These intervals only summarize maintenance services. Be sure to follow the complete scheduled maintenance on the following pages. Long Trip/Highway Definition Follow this scheduled maintenance only if none of the conditions from the Short Trip/City Scheduled Maintenance are true. Do not use this schedule if the vehicle is used for trailer towing, driven in a dusty area or used off paved roads. Use the Short Trip/City schedule for these conditions Driving a vehicle with a fully warmed engine under highway conditions will cause engine oil to break down slower. Long Trip/Highway Intervals Every 7,500 Miles (12 500 km): Engine Oil and Filter Change (or every 12 months, whichever occurs first). Chassis Lubrication (or 12 months, whichever occurs first). Drive Axle Service. Tire Rotation. 6-6