GMC 2011 Yukon XL Denali Owner's Manual page 348

10-10 Vehicle Care
Viscosity Grade
SAE 5W-30 is the best viscosity
grade for the vehicle. Do not use
other viscosity oils such as
SAE 10W 30, 10W 40, or 20W-50.
Cold Temperature Operation: In an
area of extreme cold, where the
temperature falls below 29°C
( 20°F), an SAE 0W-30 oil should
be used. An oil of this viscosity
grade will provide easier cold
starting for the engine at extremely
low temperatures. When selecting
an oil of the appropriate viscosity
grade, be sure to always select
an oil that meets the required
specification, dexos. See
Specification earlier in this
section for more information.
Engine Oil Additives/Engine
Oil Flushes
Do not add anything to the oil. The
recommended oils with the dexos
specification and displaying the
dexos certification mark are all that
is needed for good performance and
engine protection.
Engine oil system flushes are not
recommended and could cause
engine damage not covered by the
vehicle warranty.