I'm running a 180 degree T stat and no tune and no problems. Temp now stays between 190 - 200 on the highway and trans temp is 175 - 180. A few weeks after getting the truck last year, the temp would spike on the highway even when it was 40 degrees outside with the heat blasting. I'd see 232 - 240 on the coolant temp display at highway speeds and knew something was wrong. Water pump was replaced since it was leaking (no temp issues at that time) about 1000 miles before this. I bought a 180 after seeing how small the radiator is on the Expeditions and F150's (only holds a little over a gallon of coolant) and thought to go a little cooler to buy time when towing etc. I knew I must have an immediate problem with the thermostat or shutters to spike the temp on the highway like it was besides just the urge to go a little cooler for a towing buffer. When I got the old T stat pulled out, I can clearly see it was binding by the marks on its shaft. At that point I thought I wish I had an OE temp 195 to throw in but stayed the course on the 180 just to give it a try and see if the interior heat was sufficient. So far, I'm very impressed. Still great heat and no issues, even on a 5 degree day (this was a cold winter this year in the Northeast). One thing I must say is its not like the old days where a 180 T stat is 180. The T stat on these 3.5 Ecoboost engines are on the return to the water pump hose so they seem to operate a little higher than there rated temp, plus the shutters play a big mix at over riding the T stat. To me, a 180 looks to work like a 195 and so on and so forth. In the summer, I'm curious to see how this all works with the AC on and in theory it should be better since the shutters are open and fans on earlier for cooling of the condenser but time will tell. Right now, in heavy traffic, it will go to 206 then the fan is on and temp goes back down to about 195. If I get onto a highway or long enough of open road, it will fall back down to about 195. All in all, I really like the trans temp most at 175 - 180. The first three pics show the old T stat and binding on the shaft also the rubber seal is deteriorating. The last two are the new SPD 180. Note - the SPD has a Ford part number and is made by Ford so I overpaid and should of just got a Ford one! I'll do a longer write up once the weather warms up and I can evaluate this more. Another note is Ford did add a plastic sleeve to the shaft of the OE T stats as an update to stop the binding (check FordBossMe overheating after phaser repair video on YouTube). I'm not sure if that includes the 180's but for sure the stock 195's have it.
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In my opinion, these T stats to me seem to be something to replace every two or three years and not so robust to last a lifetime. Hint will be the coolant temp will spike around for no reason (just clearing a small hill or grade) when you have plenty of airflow at highway speeds.