Please check coolant level carefully. Also appearing to run cool may be a symptom of a number of things:
1) A failed thermostat stuck open
2) An airlock in the system
3) A faulty temperature sender
4) A wiring fault
5) Fan relay fault leaving the fan running constantly
Also, a noticeable variation when descending hills is abnormal
I am fairly sure that you can get temperature sensors that work on infra-red - worth taking some readings.
