1997 GMC Sonoma Owner's Manual - Page 252

Engine Oil Additives Don't add anything to your oil. Your GM dealeris ready to advise if you think something should be added. When to Change Engine Oil If any one of these is true for you, use the short tripkity maintenance schedule: 0 Driving under these conditions causes engine to oil break down sooner. If any one of these is true for your vehicle, then you need to change your oil and filter every 3,000 miles (5 000 km) or 3 months -- whichever occurs first. If none of them is true, use the long trip/highway maintenance schedule. Change the oil and filter every 7,500 miles (1 2 500 kin) or 12 months -- whichever occurs first. Driving a vehicle with a fully warmed engine under highway conditions causes engine to oil break down slower. Most trips are less than 5 to 10 miles (8 to 16 km). This is particularly important when outside temperatures are below freezing. Most trips include extensive idling (such as frequent driving in stop-and-go traffic). You operate your vehicle in dusty areas or off-road frequently. You frequently tow a trailer. The vehicle is used for delivery service, police, taxi or othercommercial application. 0 Remote Oil Filter (Four-Wheel Drive) The access door for the remote oil filter is in the steering linkage shield assembly located under the radiator support. Twist the screw to unlock or lock the door. Make sure if you open the door, it is securely closed when you are finished. 0 0 0 6-14