My experience regarding having thermostat and auto fan is excellent.
- I feel better compression (good pick).
- Engine stable quickly within 2 to 3 min.
- Heater working (no need of it but I am happy that it is also working).
- And I am sure this will also Improves fuel economy as well.
Before installing I was worried a bit, because some other guys on this forum/topic shared bad experience in which they end up with heatup issue and damage gaskit, also every other mechanic is against installing thermostat and auto fan working. But as most of the friend here recommend this I decided to do it my self.
But before doing any thing, I completely understand "how cooling system works" and what is the job of thermostat. And I also make sure my car's heat gauge is working perfectly. In the end I did it correctly.
Now I always recommend thermostat and auto fan, as it save engine and extend its life.