Cadillac 2008 SRX Owner's Manual page 277

The vehicle will automatically turn off tow/haul every
time it is started.
Driving with tow/haul activated without a heavy load or
with no trailer will cause reduced fuel economy and
unpleasant engine and transmission driving
characteristics, but will not cause damage.
Press this button, located
below the climate control
system, to enable/disable
the tow/haul mode.
A light on the instrument
panel will illuminate to
indicate that tow/haul
mode has been selected.
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.
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.
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