Factory temperature gauges give such a vague idea of engine temperature, that I only use it as a way of knowing if the engine is very hot or very cold. This is why some people buy aftermarket engine temperature gauges in older cars, and use a scan tool on OBDII cars.
Get a service manual for your truck, and find a chart that tells you the resistance of the coolant temp sensor versus the actual temperature of the coolant. If it falls outside the chart, get a new sensor, I highly recommend OEM. Other times the sensor gies an inaccurate reading because the cooling system wasn't maintained right, damaging the sensor with corrosion, or insulating from temperature change by covering it with sludge.
It wouldn't surprise me if your cooling fan clutch and thermostat need replacement. I recommend OEM only. Some aftermarket fan clutches don't even last more than 1 year.
Have you cleaned your radiator and condenser? Sometimes when they get dirty, they lose the ability to properly dissipate heat.
Are you using A/C or not? That can cause engine temperature at certain times.