i changed over to a 160 stat and it seems like i go through a 20 gallon tank in like 5 days, on a 20 mile a day commute! do i have to have a temp of 195 for my vehicle to come out of closed loop like OBD 1 cars do?

 

Yes! go back to the 195 tstat, its whats supposed to be in there. If the vehicle does not reach 195 it WILL NOT go into open loop, will run rich and you will lose gas mileage. Running rich will also cause your cat to degrade faster, and maybe even glow red hot if its rich enough, Have you noticed a sulfur smell at all after this change?
Why did you go to a cooler thermostat?
Change it back to the factory recommended (i think its 195) and you will get your MPG back..

 

i changed it cause at idle for more then 5 min in traffic it would heat up to 240 and then drop back down to 210 at 3000rpm on the freeway! it was really getting bad. i also have wut looks like hair or newspaper shavings in my radiator fluid...do u know wut it is?

 

sounds like someone put some "radiator repair" in it. I would flush the radiator, but plan on replacing it if you do. The flush may tear out the "patched" part.
Check your mech fan too...

 

actually i just replaced the radiator cause it had a leak, and i just filled the system right back up without flushing it...i think i will just flush it and change the thermostat and see how it works

 

I put a 160 Thermostat in my 97 XJ and i haven't lost any MPG, actually seems like it gets just a few more miles per tank. Should i be concerned about this?

 

thermostats are there to prevent overcooling, not overheating.

 

exactly!!! well said

If its running that warm in traffic than look into your thermal clutch fan..it may not be locking and un-locking like it should be. I just replaced mine..

 

also check you aux fan if your jeep came with one....some didnt......does it turn on after 210?

 

i don't remember if my aux fan turns on or not cause it hasnt been that hot in a while. i will check and if not then i will see about fixing that, but i am replacing mine with a 195 tomorrow

 

My aux fan doesn't kick on till about 230 degrees. Still well within safe limits. about 15 seconds after it flips on you can visibly watch the temp drop and it'll go from 230 down to 195 in less than a minute.

 

my aux fan comes on when my jeep is on and mine runs perfectly fine and cool about 195-200/210

 

I think the tstat is something like a 184? but a 190 or 195 will work great, the 4.0 is a naturally HOT engine it should read at or around 210, I live in Az and have had no problems.

 

Yeah, the stock Tstat is 195, I have a 193 in mine for winter and when the weather warms back up I'll be putting in a 180 or 175 degree tstat to help keep her cool in the summer. 4.0s are known to be a HOT running engine. Mine typically sits right at 200 or so.

 

well i have a 160 thermostat because i hate heat and heat isn't good for anything (thats my philosophy)