2003 GMC Sonoma Owner's Manual - Page 279

I I If you have the 2200 L4 engine, the engine oil fill cap is located in the rear of the engine compartment on the passenger's side of the vehicle. If you have the 4300 V6 engine, it is located in the rear of the engine compartment on the driver's side of the vehicle. When to Add Engine Oil If the oil is at or below the ADD line, then you'll need to add at least one quart of oil. But you must use the right kind. This part explains what kind of oil to use. For engine oil crankcase capacity, see Capacities and 5Specifications on page I O I. Notice: Don't add too much oil. If your engine has so much oil that the oil level gets above the cross-hatched area that shows the proper operating range, your engine could be damaged. Be sure to fill it enough to put the level somewhere in the proper operating range. Push the dipstick all the way back in when you're through. What Kind of Engine Oil to Use Oils recommended for your vehicle can be identified by looking for the starburst symbol. This symbol indicates that the oil has been certified by the American Petroleum Institute (API). Do not use any oil which does not carry this starburst symbol. 5-16