GMC 2006 Envoy Owner's Manual page 373

If the oil is below the L mark for the L6 engine or the
cross-hatched area at the tip of the dipstick for the
V8 engine, you will need to add at least one quart/liter
of oil. But you must use the right kind. This section
explains what kind of oil to use. For engine oil crankcase
capacity, see Capacities and Specifications on
page 5-119.
Notice: Do not add too much oil. If your engine has
so much oil that the oil level gets above the
cross-hatched area (F) that shows the proper
operating range for the L6 engine or above the
cross-hatched area for the V8 engine, your engine
could be damaged.
Be sure to add enough oil to put the level somewhere in
the proper operating range. Push the dipstick all the
way back in when you are through.
See Engine Compartment
Overview on page 5-12 for
the location of the
engine oil fill cap.
5-17