the thing that makes the most diff is when the fans turn on and off. even with a 160* if you set the fans high the car will get to operation temp. I have seen the best results running the engine between 185-195* so i run a 180 stat year round. my old 4t60 had slipping issues when the trans got to 190* so i ran a 160 stat and kept op temps around 170* the most important thing is to keep the coolant temp consistent. as the tables in the pcm change with coolant tempat 195 there is diff fueling and spark vs 180 or 170.
