Thermostat Temperature


Jun 24, 2019
Hi everyone, been awhile since I've posted but I've got a problem that's driving me crazy. I have a full bolt on 02 gt, fresh fully rebuilt motor, fully upgraded cooling system. I put a 180 thermostat and was instantly happier as I live in California so the colder temps help with the overall performance. The car usually hovers around 179-190 when crushing in about 80 degree weather. Now heres my issue, as soon as a little traffic hits, or it's over 80 degrees outside, the car will start hovering at 200-210, which is normal and far from overheating. The problem is that as soon as the car goes over the 195 mark, I can feel a drastic change in performance and exhaust note. I don't even look at the temp gauge when I notice the car feels different, so I know it's not placebo. Everyone always talks about how bad 160 thermostats are but never give a reason, my car runs 10x better in colder weather when the coolant temp is around 170. Summer is coming, temps are going up, would a 160 or even a 170 thermostat really hurt??
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Here is some of what is bad about a 160 deg thermostat.
The 160 degree thermostat does not get the engine warm enough to eliminate the blow by from the oil. That dilutes oil and requires more oil changes if not also making for more engine wear.
On a carbureted car, the choke might not fully open. Running rich all the time will dilute the oil on the cylinder walls and rings, and metal on metal is going to increase wear.
With FI, the engine might not get warm enough to go to closed loop operation. So it should not run at it’s best efficiency and might run rich like a stuck choke.

If it does not run right at normal the normal temp range, I suggest you have trouble shooting to do.
Don't forget your car has an air temperature sensor as well. If the incoming air is hot the computer will compensate for it too.
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Fuel injected cars want to run at 205-210 degrees for max efficiency. I don't necessarily mean fuel efficiency, but interms of proper engine clearances, proper oil temp, burning off contaminates and such from the oil, etc. Running cooler temps really isn't good for engine longevity for multiple reasons.
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It should run fine at 195-210, putting in a 160 is a band aid at best, you need to figure out why that is. I would first verify the temperature with a known measuring tool/gauge before going too far, I like to start from good "knowns" before looking for the unknowns.
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You should be running at least a 195 for a newer fuelie motor
Then if you are facing overheating issues because your motor is all bad
You add fans and coolant volume to fix that
But leave the T stat alone at 193-198 whatever one Ford parts gives you over the counter
SHO and 5L5 are on it the fuel injection will run like chit if it is not at operating temp
50Dreamer is on it too because boring the block will make more heat
You just control the heat and the hotter they run the better they run (until they blow up)