It kind of cracks me up that the simplest thing to check on anything is the temperature, whether it be outside, in the house, refrigerator, oven, your own body or even the car/truck engine.
With the proper tool(s), a temperature check is very simple, easy and accurate. If you show up to the Hospital Emergency Room or the local Immediate Care, the very first thing they do is take your body temperature.
Temperature can indicate a lot of things and quickly rule in or out potential problems.
And it just amazes me how everyone seems to convince themselves the engine temperature/thermostat is fine without every checking the engine temperature. Just see ALL the posts on VAG forums about ONLY changing the coolant sensors when a trouble code for engine temperature pops up. Not addressing the root cause of the problem. I fell victim to this foolishness and it almost cost me an engine in my 1.8t.
Freeze Frame Data for when the 1.8t finally triggered a DTC
DTC for which Freeze Frame was Stored P2181
Fuel System 1 Status Closed Loop
Fuel System 2 Status Not Supported
Calculated LOAD Value 60.00 %
Engine Coolant Temp 167.00 °F
Short Term Fuel Trim - Bank 1 1.56 %
Long Term Fuel Trim - Bank 1 -1.56 %
Engine RPM 2,000.00 rpm
Vehicle Speed Sensor 52.82 mph
My unscientific data that I have been gathering over the past few years indicates that probably over 30% of the cars and trunks on the road have soft thermostats and the engines are running too cool. This in turns increases emissions, fuel consumption, crankcase contamination and will reduce engine performance and possibly accelerate engine wear.
Do your car a favor, check the temperature often and know where the benchmark temperature operates. Do not get fooled and think the thermostat is good then find out in the middle of the Winter that you have a bad thermostat. Keep a close eye on the engine temperature when the weather starts to cool off and/or use a garden hose to super cool the radiator and see if the engine temp is maintained or if it drops.
Nothing worse than having a bad thermostat in the middle of Winter and trying to change it when the weather is close to freezing and you are dealing with antifreeze on your tools and hands.