Would a cooler running engine (from 195 to 180) make a real significiant difference in the oil flow through an engine using a recommended 10W30 oil?

Come the winter months, here in the NY Metro area, would it simply be better,instead, as a compromise, to switch to a lighter 5W30 oil in winter and keep the 180 in year round instead of opting back to tyhe 195 stat?

The oil flow difference between 180 and 195 is negligible. How well the oil flows at 20 below is the issue. The main reason you might want the 195 in the winter is to get more heat.

With the 195 t-stat your car will heat faster in the winter. So if you like it nice and toasty in the winter, the 180 will take longer to get warm air in the car.

I had my 180 stat in the winter too, and use 5W-30 in the winter. I hate taking apart my stat housing and losing coolant all over the place. I've already done it twice. So I leave it in.

Living in Syracuse, which has somewhat colder winters than people living in the NY/NJ Metro area, for sure, is the heat in the car that much more noticeable to the point where you wind up wishing the hottoer stat were back in?

I know these 1992-99 Bonnevilles (as well as the 88s and LeSabres) can toss out some serious hot air...But with the 180 stat I also noticed that my windshield (outside) doesn't fog that much in hot/humid weather, which was obviously from the engine running hooter. Though it could just be my imagination.