I'm running a 180* thermostat that I got from lingenfelter.

There is a big debate on whether a 160* thermo is to cold for the gen III-up engines so you might want to do a couple of searches before you decide on one. Basically what I got from all the debating & research was that the LS engine likes to run hotter than the older generation motors. The engine also needs to get up to a certain temperature to burn off any condensation that is in the oil which the 160* may not allow in real cold climates. I think it was zippy who did a lot of testing on where a naturally aspirated LS engine makes it's peak power and it was between 170*-180* if I remember right. Given that your coolant temp will be a little warmer than your thermostat, I think that in most cases a 160* will be best in the summer and the 180* for the winter. My truck is my DD so I just keep the 180* in year around so I don't have to mess with the tune/changing the thermostat and fluids. I am in no way an expert on this subject this is just my assumption based upon what I have read.

 

LOL, because that t-stat and dexcool is expensive I've been holding off until I build the LQ9...but, who knows when that will happen

 

Hope this helps