1993 Buick Park Avenue Owner's Manual - Page 299

Selecting the Right Schedule First you'll need to decide which of the two schedules is right for your vehicle. Here's how to decide which schedule to follow: If any one (or more) of these is true for your driving, follow Schedule I. Schedule I1 Follow Schedule I1 only if none of the above conditions is true. Schedule I Is any one of these true for your vehicle? Most trips are less than 4 miles (6 km). Most trips are less than 10 miles (16 km) when outside temperatures are below freezing. The engineis at low speed most of the time (as in door-to-door delivery, or in stop-and-go traffic). You operate your vehicle in dusty areas. You tow a trailer.