1999 Buick Riviera Owner's Manual - Page 323

yellowblue Short Trip/City Scheduled Maintenance - In hilly or mountainous terrain. - When doing frequent trailer towing. - Uses such as found in taxi, police or delivery service. If you haven't used your vehicle under severe service conditions listed previously and, therefore, haven't changed your automatic transaxle fluid, change both the fluid and filter. DATE ACTUAL MILEAGE j 150,000 Miles (240 000 km) j Drain, flush and refill cooling system (or every 60 months since last service, whichever occurs first). See "Engine Coolant" in the Index for what to use. Inspect hoses. Clean radiator, condenser, pressure cap and neck. Pressure test cooling system and pressure cap. An Emission Control Service. SERVICED BY: 7-21