1995 GMC Sonoma Owner's Manual - Page 227

When to Add Oil If the oil is at or below the ADD line, then you'll need to add some oil. But you must use the right kind. This part explains what kind of oil to use. For crankcase capacity, see "Capacitiesand Specifications" inthe Index. NOTICE: Don't add too much oil. your engine has much oil that the If so oil level gets above the cross-hatched area that shows the proper operating range, your engine could be damaged. The engine oil filler cap is located on the driver's side engine valve cover. Just 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 Oil to Use Oils of the proper quality for your vehicle can be identified by looking for the "Starburst" symbol. The "Starburst" symbol indicates the oil has that been certified by the American Petroleum Institute (API), and is preferred for use in your gasoline engine. If you change your own oil, be sure use oil that has the "Starburst" you symbol on the front of the oil container. If you have your oil changed for you, be sure the oil put into your engine American Petroleum Institute is certified for gasoline engines. 6-9