Anyone try a 160F thermostat?

These are often touted as a performance mod to change the computer settings. It just seems way to cool for a 4.0 to me, I even wonder if it could keep it that cool anyway. I'm looking for first hand experience hear, if ya did it what were the butt-dyno results and what kind of temps did it run? TC

well I ran one for awhile. Butt dyno said that with my exhaust, intake and other mods I needed more fuel for power. Fuel mileage said I didn't get any worse than before. Yes it did run at 160 and not much above that... ever! I have since switched to a 180 then when it froze I put a stock 190 in.


To me it seems the 4.0 likes the cooler temps. Before I switch back to a 180 I am going to insulate my intake to see if that helps the butt dyno any. Maybe it just likes the cooler air.

The engine was designed to run with a 195 degree thermostat. The 165 is right on the line where the ECU switches from open loop to closed loop. Under many conditions, then, with that stat you will not be using the computer to control your fuel injection, you'll be running rich in the "warm up" mode.

This so-called "mod" is a serious mistake. The lowest you should go is 180, and IMHO even that's amistake. If the cooling system can't control overheating with a 195 degree t-stat, running a colder t-stat can only depay the overheating by a few seconds at best. Better to run the right t-stat and address the cooling system.

Sorry Eagle, but I have to disagree. I am currently running a 180* stat in my 4.0 and have been nothing but pleased with the results.

Does it cool better than it did with the 195*? No, of course not.

But, the engine runs as well as before with no apparent over-rich fuel mixture. Under the hood stays much cooler for 95% of your daily-driving, which can only help to extend the life of any hoses/wires in there. And, the few second buffer you mention is more like 45 sec or so, which is long enough to keep you under 210* on the gauge while pulling a load up a short hill.

Overall, it only works better for me. No disadvantages whatsoever and like I say, I stays a lot cooler most of the time.

Just don't expect a lower temp stat to cure your plugged radiator and you will be pleased with the results.

I agree with Eagle that the 160* would be a mistake. Forcing the Jeep to run in "warm up" mode all day would be rather foolish. But I say where the 180* is concerned, go for it.