a 195 stat is for a V8, if you use your 235 much in winter a 180 will keep the heater working well, and a 160 would be fine for summer with occasional cooler weather use, a 195 is keeping the engine [and lubricating oil] hotter than necessary
the way a thermostat works is to open within a couple degrees of the rated temp and close again if the temp falls below that, a 160 could be cycling in very cold weather unless you have a rad curtain and the engine will be running a bit cool
Bill
