I know that switching to a cooler thermostat is supposed to increase power slightly, but in keeping the engine cooler, won't fuel economy decrease because more heat = better fuel atomization? Or am I completely off-base on this one?

 

I've never noticed a difference either way (fuel or performance) but I still do it anyway.

 

Its good and bad:

On the plus you will get a slight gain in performance (most noticable in the summer). Some other larger mods like a mopar PCM require the 180 due to the air fuel mix.

The down side is the mpg will go down a little, and if you dont have the performance PCM the cooler t-stat may cause your motor to run in wide open loop (think thats the term) causing you to run rich.

 

I've been told by a mechanic friend that the 180 t-stat will not send the pcm into open loop mode. I had just the 180 stat in my jeep GC 318 & it passed easily here in CA. He mentioned that if you went to the 160 it would stay in open loop.

 

It may be truck to truck. Guy on another site had the 180 and it kept him in open loop (99 Ram 5.2). When I first did mine I had no problems either

 

I wonder if there might have been something else going on w/his truck. Or maybe they changed the stock programming (my jeep was a 93).

Did he mention how he knew it was in open loop? CE Light?