1998 Buick Century Owner's Manual - Page 330

I MaintenanceSchedule I 45,000 Miles (75 000 km) 0 Check Oil LifeMonitor. If engine oiland filter are changed,reset monitor. See "Engine Oil" in the Index. An Emission Control Service. (See footnote*.) 0 Inspect air cleaner filter if you are driving in dusty conditions. Replace filter if necessary. An Emission Control Service. (See footnote "F) 0 Replace passenger compartment air filter. 0 Rotate tires. See "Tire Inspection and Rotation" in the Index for proper rotation pattern and additional information. (See footnote+.) 50,000 Miles (83 000 km) 0 Change automatic transaxle fluid and filter if the vehicle is mainly driven 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. I f you do not use your vehicle under any of these conditions, the fluid and filter donot require changing. 7-8