BuckB91XJ

I have a question to pose to all you XJ pros here on the CF.

I have read many threads on many forums about how guys had replaced their OEM 195 degree T-stats with 180 degree T-stats. This worked really well for keeping their XJs, with the 4.0 motor, from overheating in the summer and still kept the heater pretty warm in the winter. Common sense also told me that a motor running a little cooler would last longer. I was then told by a mechanic at a Dodge dealership that the the 4.0 Jeep motor was designed to run all day long, in hot or cold temperatures, with the OEM 195 degree T-stat. he also said that changing to a colder T-stat would degrade how the motor performs I.E. fuel mileage and power would suffer.

What are you guys' feelings on this subject? I still have the 180 degree T-stat in my motor. It has been in there for a couple of years now. If I can squeeze a few more MPGs or more power out of my XJ then I'm considering putting a 195 degree T-stat back in.

lil'whiteXJ

I put a 195 in mine not too long ago. I did it for more heat (I live north of Spokane) and I have noticed better mileage, and less exhaust when it is real cold.

cherokeefamily

My advice...make sure you're auxillary fan is working and then use the 195.

BowtieGuy3

I just replaced the stuck factory one in my 98 with a 180*, and it works great, it rarely gets to 210 now, and I still have heat. It takes a little longer to warm up the inside, but other than that I haven't noticed a single drawback to the 180's. A 170 or 160 prob would be a little much, but a 180 is fine.

BlueXJ

FSM calls for a 195.

93XJLI

Which is why its the only one that should be run.

BuckB91XJ

Well, my current set up has LOTS of power and I get 22 highway/16 city. I suppose I should go back to the 195 stocker since it's the only one that should be used.