1997 Buick Riviera Owner's Manual - Page 324

I Short Triplcity Maintenance Schedule I 27,000 Miles (45 000 km) 0Change engine oil and filter (or every 3 months, whichever occursfirst). An Emission Control Service. 24,000 Miles (40 000 km) 0Change engine oil and filter (or every 3 months, whichever occursfirst). An Emission Control Service. El Lubricate chassis components every (or 6 months, whichever occurs first). (See footnote#.) 0Rotate tires. See "Tire Inspection and Rotation" in the Index for proper rotation pattern and additional information. (See footnote+.) I ACTUAL MILEAGE SERVICED BY: 1 DATE ACTUAL MILEAGE SERVICED BY: 7-11