From the parts list, there are two thermometers. One is 180 degrees SBA145206182 and the other is 190 degrees and SBA145206130. If you have a severely cold winter and your tractor does not warm up enough, I'd go with the 190 degree thermostat. If your tractor is getting up to temperature okay in the winter, then it's common to just leave a 180 degree thermostat in year-around.