Jaguar F-Pace 20d AWD Prestige, 132 kW.

Friends, I'm solving a cold engine problem on my wife's car. Even on a longer drive (distance approx. 40 km, speed 90 km/h) the coolant temperature on the clock is just above the blue value.
If I increase the speed to approx. 160 km/h then the engine starts to warm up, but the indicator rises to approx. 1/4 of the range, and is well below the "warmed up" engine, roughly in the middle of the range.
If I slow down back to 90 km/h, the indicator returns almost to the blue field, meaning the coolant temperature drops almost to the initial value of a cold engine.
I'm looking for the cause, I've ruled out a completely bad thermostat, but it could be stuck. Maybe.
The question is where to start, and how many thermostats are in the engine, I assume about 2.
Or go some other way?

Thanks Roman

 

Yep, thermostat is sticking open or your coolant temp sensor is failing, I would assume the t-stat. Left side of the engine right on the block.