GMC T-Series 2007 Owner's Manual page 207

When to Add Engine Oil
Notice: Do not add too much oil. Keep the oil
level between the ADD and FULL marks on
the dipstick. Under normal engine operation,
the engine oil level can increase above the
FULL mark as a result of DPF regeneration.
A small increase in the oil level is normal.
If the engine has so much oil that the oil level
reaches the wider portion (A) on the dipstick,
the engine oil must be changed as soon
as possible or the engine could be damaged.
If the oil is below the
ADD mark on the
dipstick, you 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 285.
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.
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