Chevrolet Silverado Classic 2007 Owner's Manual page 216

With cruise control, the vehicle can maintain a
speed of about 25 mph (40 km/h) or more without
keeping your foot on the accelerator. This can
really help on long trips. Cruise control does not
work at speeds below about 25 mph (40 km/h).
If you apply your brakes, the cruise control
will shut off.
CAUTION:
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Cruise control can be dangerous where
you cannot drive safely at a steady speed.
So, do not use your cruise control on
winding roads or in heavy traffic.
Cruise control can be dangerous on
slippery roads. On such roads, fast
changes in tire traction can cause
excessive wheel slip, and you could
lose control. Do not use cruise control
on slippery roads.
216
Setting Cruise Control
CAUTION:
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If you leave your cruise control on when
you are not using cruise, you might hit a
button and go into cruise when you do
not want to. You could be startled and
even lose control. Keep the cruise control
switch off until you want to use cruise
control.
1. Move the cruise control switch to on.
2. Get up to the speed you want.
3. Press the set button at the end of the lever
and release it.
4. Take your foot off the accelerator pedal.