Mazda CX-5 2018 Owner's Manual page 324

Always turn off the cruise control function
when it is not in use:
Leaving the cruise control function turned
on when it is not in use is dangerous as it
could operate unexpectedly, resulting in an
accident.
NOTE
The system may not be able to maintain
•
the set speed constantly depending on
driving conditions such as steep up or
down slopes.
The speed will continue increasing while
•
the SET switch is pressed and held.
The speed will continue decreasing
while the SET switch is pressed and
held.