Over cooling!

As a general rule for people that don't have a lot of experience with it, your car isn't running too hot if it doesn't blow fluid out when you stop. (The coolant temp in the engine increases when the engine is shut off) and that is when you know for sure it's running on the hot side.

I also agree that 160 is too cold and increases engine wear.

Personally I run a 190 year round here in AZ.