Coolant Temp - Changes

So with the OBD scanner in the car my coolant temps ranged from 70 to 89 and that was after driving for at least 30 mins, would drop down on the freeway but to 70 degrees? And then in traffic up to 89 at max

The car is not over revving on idle sits at about 890RPM, no fault codes are shown on the scan tool.

This cannot be normal, for the coolant temp to range this much, when reading from the OBD what would send the info to the ECU for coolant temp? Is it the coolant temp sensor as I don't think nearly 20 degrees of fluctuation once the car is warm is normal.
 
My temperature varies between 80-91°C (when idle).

Thermostat closes @ 75°C and opens @ 87°.
 
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Just seemed like a wide band high to low temp. If I drop to under 70 or over 100 I'll act.

Can check fault codes and all fine currently.