1998 Buick Skylark Owner's Manual - Page 238

What Kind of Engine Oilto Use Oils recommendedfor your vehicle can be identified by looking for the "Starburst" symbol. This symbol indicates thatthe oil has been certified by the American Do Petroleum Institute (API). not use anyoil which does not carry Starburst symbol. this If you change your own oil, be sure you use that has oil the Starburst symbol on the front of the oil container.If you have your oil changed for you, be surethe oil put into your engine is American Petroleum Institute certifiedfor gasoline engines. You should also use the proper viscosity for your oil vehicle, as shown in the following chart: 3100 Engine The engine oil fill cap onthe 3 100 engine is located at the front of the engine near the engine oil dipstick. Be sure tofill it enough to putthe level somewhere in the proper operating range. Push the dipstick all way the back in when you're through.