These are only ideas and suggestions not to be necessarily an actual cure for the problem because of the limited technical information and observations posted about the problem:

Before everyone jumps to condemn the thermostat which BTW seems to me to be correctly working, may I suggest to attach a piece of cardboard in front of the grill and do a few test drives. Then see what happens? I would also try to keep the defrost off if possible or turn off the AC if the light is on indicating the AC is on because of the fan actuation when the AC compressor works.

I run a Modified -170F( Proprietary design) thermostat and and have traveled in some cold climates that got as low as high teens low 20's. Not 3F like the OP but still cold. My engine temperature would be around 140F-155F. No check engine light. The warm up took longer if I idled the car after start but would still go out of closed loop into open loop @ 129.7F (130F) in about 3-5 minutes of easy driving.

 

Thanks Callisto,
I made the test today. Next conclusions are:
Normally I drive about 110km/h, today I drove a little faster (about 160km/h) and after couple of minutes I had abou 200F and then when I stopped and wait couple of minutes, the temperature was still about 200F, didn't fall down.
Hmmm, strange,...I don't won't to give the car to Dealership because I'm almost sure that they will investigate it only with computer and guilty will be the whole coolant control valve (thermostat cannot be replaced separately).

 

Next observation.
I started engine and didn't drive. I waited about 10 minutes and the temperature increased to about 195F so the optimal one.
When I started driving, after 1-2 km the temperature decresed to about 150F, when I stopped and wait, the temperatyre started to increase again.
So this is not good news because it means that thermostat is opening and not closing when the temperature is decreasing, almost 750EUR (together with installation) to spend...

Maybe anybody has different idea?

 

No that"s not what it means....

going to 150F is not unusual given you ambient temperatures. Besides what just post is what I get every morning here in US of A California and my ambient temperature's in the morning going into work are only 46F average.

I suggest to invest in a hand help thermal reader and see what all your temperature's independent of the ECU or dash is indicating.

I did not actually read you took my suggestion in my last response?

 

Really? So the temperature can fall down during normal speed about 90km/h? I didn't know that.
Defrost and AC is off. I will check the cardboard.
Thanks.

 

while I give NO guarantee's and as I am only advising and suggesting things based on your observation and what you post I have yet read anything that would cause me "PERSONALLY" a concern except if me temperatures inside the cabin were not getting warm enough. hahaha!

ASE L1 & L2 Certified

 

The temperature inside the car is very ok (warm is getting fast), no problems with it. Generally I don't see any problems besides this "check engine".

So there is no other disadvantages of keeping the engine with 150F? I mean carbon deposit on the pistons, oil is not to dense, etc?

I'm not good in car mechanics, that's why maybe stupid questions

 

I would suggest to invest in a diagnostic tool that you can PLUG in to the OBDII diagnostic connect to retrieve DTC and to clear and or re-set the DTC and monitors .
The temperature is the coolant not the combustion chamber temperature's that would effect things like carbon formation. If you took a tail pipe thermal reading you would see that after a 15-20 minutes of normal driving the exhaust temperatures would be right where they should be.

Oil is not described as dense or less dense but in viscosity often miss termed as thicker and thinner. The "W" stand for a winter blend or combination of oil viscosity values i.e. 0W30. And here again the oil temperatures are more influenced by the engine combustion temperature not as must by what the coolant temperatures is. So for the oil to do it job you only need to run the engine 20-30 minute's.

Back to a DTC..... DIY and poorly trained mechanics will jump to a bad conclusion to change a part (hit and miss method of problem solving) instead of doing the proper problem solving and testing tree as outlined in most every Factory Service Manuals for at least the last 30 years. So I always recommend to people to find a shop that either has w FACTORY TRAINED Auto Technician or a certified ASE Automotive Technician. Please note I did not say a MECHANIC!

 

ok, clear to me, thanks, less worries better weekend 😀
Moreover I use oil 0W20 so lower temperatures are better 😂
thanks again and have a good weekend

 

Hi,
next conclusions.
Mechanics checked the temperature with computer and it's the same like on the gauge.
Next ​I drove to the city and in the traffic the temperature increased to about 200F and stayed on this level until I left city center and drove on the highway, again 150F.
When I came home I stopped and checked the temperature of the liquid by the device and the temp. was the same like on the gauge.
I didn't turn off the engine, after couple of minutes I had 200F.
The coolant control valve?