A 160 will fully open at 175 and if all other things in the cooling system are equal, engine size, hp, transmission, ambient air temp etc, will stabilize at the same temp as a 180. A 160 was never run factory on a Mopar. It is an aftermarket rating marketed to the internet/shade tree "Phd's". People noticed their engine reved quicker, felt snappier when it was 1st started/cold. This wasn't due to the engine being cold, but to the cooler/denser air. As the engine warmed up, so did the air intake and the air wasn't as dense. But those Phd's thought it was the cold engine.