GMC 2007 Yukon XL Owner's Manual page 408

Tow/Haul is most useful under the following
driving conditions:
•
When pulling a heavy trailer or a large or
heavy load through rolling terrain.
•
When pulling a heavy trailer or a large or
heavy load in stop and go traffic.
•
When pulling a heavy trailer or a large or
heavy load in busy parking lots where
improved low speed control of the vehicle is
desired.
Operating the vehicle in tow/haul when lightly
loaded or with no trailer at all will not cause
damage. However, there is no benefit to the
selection of Tow/Haul when the vehicle is
unloaded. Such a selection when unloaded may
result in unpleasant engine and transmission
driving characteristics and reduced fuel economy.
Tow/Haul is recommended only when pulling a
heavy trailer or a large or heavy load.
408
Weight of the Trailer
How heavy can a trailer safely be?
It depends on how you plan to use your rig.
For example, speed, altitude, road grades, outside
temperature and how much your vehicle is used
to pull a trailer are all important. It can also depend
on any special equipment that you have on your
vehicle, and the amount of tongue weight the
vehicle can carry. See "Weight of the Trailer
Tongue" later in this section for more information.
Maximum trailer weight is calculated assuming
only the driver is in the tow vehicle and it has all
the required trailering equipment. The weight
of additional optional equipment, passengers and
cargo in the tow vehicle must be subtracted
from the maximum trailer weight.
Use one of the following charts to determine how
much your vehicle can weigh, based upon
your vehicle model and options.