I was thinking the same thing. There would be a heat differential. The fans would kick on based off of temperature before the thermostat. I don't know how much of a difference that would make. The t-stat opens at a certain temp...the fans would kick off around 170 or thereabouts. I'd have to look at the specs. Maybe i'm thinking too much about it. Anybody know the engine side and post t-stat side heat differential?