Buick 2007 Rainier Owner's Manual page 370

When to Add Engine Oil
L6 Engine
V8 Engine
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.
370
This section explains what kind of oil to use. For
engine oil crankcase capacity, see Capacities and
Specifications on page 474.
Notice: Do not add too much oil. If the 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, the 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 366 for the
location of the engine
oil fill cap.