Digital thermostat gun 

Great tool to have for troubleshooting and finding potential issues on your truck. I use this for a number of things while looking for issues on the truck and post tripping.
Helps if you do not have differentials sensors for temperature also, helps you determine exhaust temps and troubleshooting your air conditioning in your truck. Many uses for this thing
Amazon sells them, Walmart in the BBQ section and home Depot ...prices vary. Amazon was cheapest