My commander coolant temp usually reads 15deg or so cooler than the outside air before I start the truck for the first time of the day. Is this common? Should I add 15 or whatever to everything it says? Normal warmed up temp shows about 180-190 not towing.

 

A lot of times the sensors are not calibrated on the low side. They are meant to be accruate on the high side.

 

That is a bit of an oversimplification. 15 degrees a significant error percentage wise on the normal scale of the coolant temperature. I also doubt that it is a linear error so you can not just add the noted error to the actual reading to correct. I would have it checked.

 

Its possible that everything is reading fine. Since you are starting it in the morning the coolant reservoir could actually be cooler then the ambient air. Basically, the coolant temperature can still be representing the colder air from the middle of the night. Air warms alot faster then water does... I guess it all depends on the time that you are starting up the truck and how much warmer it currently is from overnight low.

 

Good point, but it usually reads lower than the overnight low temperature.

 

FWIW my SPA EGT and tranny temp gauge usually read exactly the same first thing in the morning, which is right around the ambient temp.

 

Mine do too, but my ECT on my Quadzilla(this morning) read 36*. The outdoor temp was 47* or so. I've heard from Quad the same as what chrleb1 said, the sensors are designed to be more accurate in the range we need them most.

 

The normal warmed up temp you listed seems low to me. Mine has always been in the 200-205 range