Thermostat 180 or 195? 4.0

My 93 XJ runs on the hot side like everyone elses.
I am going to put a 3 row radiator in it.

However, I was also thinking about putting a 180 degree thermostat in it instead of a 195. Has anyone noticed any problems passing emissions and/or decreased gas mileage with the 180?

just did that same thing last summer when mine over heated one day after my lil bro turned the a/c on whiel it was sitting in the hot GA sun with the windows up. it runs fine and passes emissions no porblem but as for gas mileage im not too sure cuz i didnt really check mileage all that much until gas prices sky rocketed durin the time of Katrina. but i have heard that it should get worse but my XJ is a 97 4.0 3.5" lift 31s and factory gears and if i drive easy i can still get 14.5 mpg city but if i sit in traffic alot or drive a lil harder its more like 13.5. hope that helps

there should be a few threads on this topic out there, I read one just the other day asking same thing, including the 160 degree one aswell.
mixed opinions, the 3 row may or may not solve your overheating problems. is something wrong with the thermostat you have in there now?
if not keep it and see how it works. I just replaced mine today actually, after an overheating trail run last weekend, I went with the 192 as popular opinion said thats what stock is, stick with it.
If you over heat with the 192, the 180 will only prolong the time to overheat by a few minutes. If it runs too cool (180 shouldn't I don't think) then your gonna loose mpg as the engine runs in warm up mode which in turn means running rich (if memory serves correct)
hope that helps

Beakie is right. If it overheats with a 195 it will overheat with a 180. The thermostat only keeps it from running to COOL, not from running too HOT.

On the other hand, a 180 thermostat isn't low enough to really hurt anything. If it lowers your gas mileage it would probably be by something like 0.001 MPG. Barely measurable.

I run a 195 in mine, it typically gets up to about 210 and then hovers there. That's good for me.

dmillion said:

Beakie is right. If it overheats with a 195 it will overheat with a 180. The thermostat only keeps it from running to COOL, not from running too HOT.

On the other hand, a 180 thermostat isn't low enough to really hurt anything. If it lowers your gas mileage it would probably be by something like 0.001 MPG. Barely measurable.

I run a 195 in mine, it typically gets up to about 210 and then hovers there. That's good for me.

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That really depends. If the motor runs too cool then it will stay in open loop mode and it will have poor gas mileage. Temp for the ECU to come out of open loop is about 170. So that leave you 10* between running fine and running in open loop.
Fix the root cause of your overheat, then use a 195 like it was designed to have.