1997 Buick Century Owner's Manual - Page 351

I Short TripKity MaintenanceSchedule I 81,000 Miles (135 000 km) 0Change engine oil and filter (or every 3 months, whichever occurs first). An Emission Control Service. 78,000 Miles (130 000 km) 0Change engine oil and filter (or every 3 months, whichever occurs first). An Emission Control Service, El Rotate tires. See "Tire Inspection and Rotation" in the Index for proper rotation pattern and additional information. (See footnote +.) DATE ACTUAL MILEAGE SERVICED BY: DATE MILEAGE ACTUAL SERVICED BY