GMC 2.8L Duramax Diesel 2020 Manual page 29

28 Driving and Operating
Caution
Do not mix fuel with DEF, and do
not put DEF in the fuel tank. This
could lead to costly repairs that
might not be covered by the
vehicle warranty.
Diesel Exhaust Fluid (DEF) is used
with diesel engines to reduce the
amount of regulated emissions
produced. Products such as AdBlue
are types of DEF, and are approved
for use in the vehicle as long as
they have an API certification label
or meet ISO 22241. The fluid level
in the DEF tank must be maintained
for the vehicle to run properly. DEF
is not a fuel additive. DEF should
not be mixed with or added to diesel
fuel. DEF freezes when exposed to
temperatures below 11 °C (12 °F).
For DEF tank capacity see
Capacities and Specifications 0 97.
It is normal to hear the DEF system
purge fluid back into the tank after
the vehicle is shut off.
Locating Diesel Exhaust Fluid
DEF can be purchased at your
dealer. Additionally, some diesel
truck fueling stations or retailers
may have DEF for purchase. For
vehicles with an active OnStar or
connected services plan, OnStar
can help to locate a DEF retailer.
See Customer Assistance Offices
in the owner s manual for phone
numbers to assist in contacting a
GM dealer. See Recommended
Fluids and Lubricants 0 93.
Filling the DEF Tank
DEF Fill Van Model Shown,
4-Cylinder Pickups Similar
The blue DEF cap is behind the
fuel/DEF door. Do not remove the
fuel and DEF caps at the same
time. Fill diesel fuel and DEF
independently. Turn the DEF cap
counterclockwise to remove.
In cold conditions DEF can freeze in
the DEF fill pipe opening. If this
prevents the filling of the DEF tank,
place the vehicle in a warm garage
overnight.