2003 GMC Envoy Owner's Manual - Page 311

V8 Engine L SAE 5W-30 The engine oil fill cap is located in the engine compartment toward the passenger's side of the vehicle. See Engine Compartment Overview on page 5-72 for more information on location. 7 When to Add Engine.Oil If the oil is at or below the F mark for the L6 engine or the cross-hatched area at the tip of the dipstick for the V8 engine, then you'll need to add at least one quart of oil. 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. 5-16