I am not sure i follow the idea here. Is your car not slowing (ie if set to 45 and you go downhill it increases to 50+) or is it slowing to maintain the set cruise (if set at 45 stays 44-46)?
In my 2016 1.5T the cruise slows the car down using a lower gear when going downhill if the speed increases 2-3 mph above the set speed. If I set 45 it will maintain 44-46 mph up or down hill. Other users ( not me) have actually posted complaining about this as they would prefer the car roll downhill and not force slowdown. In the thread linked below, a 2019 owner complains about the car slowing to maintain speed when in cruise. My 2016 does the same. It would seem odd if not a malfunction if a 2018 was doing something different.
See this thread: https://www.chevymalibuforum.com/threads/cruise-control-braking.116201/
In my 2016 1.5T the cruise slows the car down using a lower gear when going downhill if the speed increases 2-3 mph above the set speed. If I set 45 it will maintain 44-46 mph up or down hill. Other users ( not me) have actually posted complaining about this as they would prefer the car roll downhill and not force slowdown. In the thread linked below, a 2019 owner complains about the car slowing to maintain speed when in cruise. My 2016 does the same. It would seem odd if not a malfunction if a 2018 was doing something different.
See this thread: https://www.chevymalibuforum.com/threads/cruise-control-braking.116201/
