1997 Buick Century Owner's Manual - Page 359

I LongTripmighwayMaintenanceSchedule I 30,000 Miles (50 000 km) 0Change engine oil and filter (or every 12 months, whichever occurs first). An Emission Control Service. 0Inspect fuel tank, cap and lines for damage or leaks. Inspect fuel cap gasket for any damage. Replace parts as needed. An Emission Control Service. (See footnote?.) 0Replace passenger compartment air filter. 0Rotate tires. See "Tire Inspection and Rotation'' in the Index for proper rotation pattern and additional information. (See footnote +.) 0Replace air cleaner filter. An Emission Control Service. I DATE I ACTUAL MILEAGE ISERVICED BY: I 7-29