Or is there a 19? t-stat that will work like all my other vehicles and maintain at it's setpoint?

I've got 95% of my grill blocked off to air flow and after an hour of driving 55mph she's still running in the 160's sometimes cresting 170. If I push it to 75mph then it will warm up to the mid 180's. But I drive mostly back roads.

I've got the Ford 192 t-stat in there now and when towing it runs 190's - low 200's. Sometimes higher when climbing mountains, so I really don't feel like switching back and forth between 203 and 192, empty vs towing.

I am really only asking since I can see a drop in mileage when it's running in the 160's vs 190's, about 1-2 mpg. Doesn't sound like much but it's a 8-13% drop.

Why does the Ford t-stat run at such a lower temp than set point, this is my second one and they perform the same. I can literally trend my temp with my speed/rpms 55mph = 160's. 65mph = 170's. 75mph = 180's with outside air temp of 30.

In the summer 100+ temps just increase those temps by 10 degrees.

I know I'm being a little picky but every other vehicle I've owned always ran at the t-stat setpoint not 30 degrees below. I know it always allows some bypass flow so there's no hot spots but it shouldn't be that much.

 

If your engine won't warm up all the way, then it shouldn't matter which thermostat you use because neither one should ever open.

Kind of sounds like you've got a thermostat that is partially stuck open and not closing off to let the truck warm up.

 

Before jumping into solving a coolant temp mystery: Where is this temperature information coming from? Our trucks don't have reliable ECT information on the OBDII port. I've always found my coolant to be within about 10 degrees F of the engine oil temp (confirmed with IR and laser thermometers).

 

I'm ruling out a stuck open t-stat since this one performs the same as my last one. Just seems like the people with a 203 report like it stays closed longer or opens closer to setpoint than this Motorcraft 192.

And can anyone explain to me better about these long stem t-stats. Does that spring loaded bypass keep it closed at idle but open when at driving rpms under higher water pump pressure. And then the temp side opens when it gets "closer" to the temp setpoint for more flow?

And you're right Tugly I'm going off my Scangauge II but in the summer it's withing 5 degrees of my Laser temp gun so it's at least pretty accurate when warmer. I haven't used the temp gun when it's colder (160's-170's). But oil temp on the Scangauge follows right along 13-16 degrees warmer than coolant temp. This morning on the way home (nightshift on Thanksgiving) ECT was 170 and oil was 185. 38 degrees outside.

 

Forget it, the more I read about the 203 it will work for empty driving in the cold but people see higher oil and water temps when towing and I tow around 12,500#'s once every month or 2 so I'd have to switch back and forth every time and then back to the 192 for the AZ summer.

Guess my wife was right when she said "just shut up and drive it". Don't tell her I said that.

 

...if I had a nickle for every time I heard that here....

 

Hahaha, I couldn't resist it!

 

To keep temps in balance I monitor the EOT. I use cardboard between the radiator and the Air intake cooler. Have to move the wiring harness out of the way to install. During the winter I have to drive with the radiator mostly covered, Guesstimating 95 to 98 percent covered. This is at 65 to 70 MPH on interstate. Now while towing a different story, I usually take out all restriction of airflow to keep temps in line. I adapt per outside temps. I don't know if it makes a difference if blocking off the grill vs blocking off the radiator and air intake cooler..... This is going off my Scanguage II.

 

I live in AK.

During the winter I run a winter front on my truck to cover the entire grill. It also has a flap that pulls down and covers the trans cooler. That flap makes a huge difference.

Before I had this one made, I ran one that just covered the radiator and barely made a difference.

I monitor both my EOT and trans temp via Areoforce gauge. I also have Isspro Coolant Temp and Transmission temp gauges. The coolant temp is usually within 10-15* of my EOT, which is what I monitor the most.

While driving around town, after about 20 or so minutes, my EOT will be up to 201-203*. If it idles for awhile it'll drop back down to 180-190 but I don't worry about it too much.

While towing the winter front has to be taken off or things will get hot very fast.

My truck averages 10.5 MPG but I tow and idle a lot. Heavy towing I can drop down to 7 or 8mpg (15k through mountains) When I'm not most of my driving is city. It's a 7500lb moving brick, so I'm not expecting good mileage. Running empty on pure highway I can get 15-17 depending on conditions. I've had two other 7.3 PSDs and they've all gotten similar mileage.

My advice- get a custom winter front made with the flap that extends down over your trans cooler. Check tent makers, they can make them easily and cheap.

 

I run a 203 t-stat year around, towing or not.
EOT of 220 is not too hot. The 2012 Mack I drive at work runs 240 oil temp all day.

 

^WHS.

I think the 203* is the cat's azz. Love it. Given it doesn't get as hot up here, but I've never had any issues, and unless your oil is getting in the 240*+ range, I wouldn't even worry about it.

 

I've had my oil in the 240's with the 192 t-stat but I was running her hard towing 13k. Which shouldn't mean it would be any higher since the t-stat is already wide open well before that.

But I think I'm gonna stick with the 192 since in these AZ summers I'm bouncing on and off the fan clutch even when empty in town.