I have been running the 203 t-stat for about 40,000 miles, and I haven't really noticed much difference. Maybe a little more cab heat. Not enough change in engine temp to see a difference on the factory temp gauge. But, I don't really tow, so the idea of a t-stat that is letting my engine warm up a few degrees more does appeal to me. I'm happy with it. Another suggestion, buy the billet t-stat housing Bob sells. The stamped steel factory ones never reseal and you end up buying a new one every time you take it off. Spend the money for the billet one and never have to replace it again.