I have owned my 2020 Mercedes CLA250 for 6 months, the mileage is about 14,000. I started noticing the thermostat was creeping up over the half way mark, even after the weather started cooling down so it struck me as odd. Few days later, shortly after starting the car (had been sitting for 8 hours) I noticed the temperature gauge quickly shot up to red then back down to the halfway mark. Stayed at half way for the remainder of my drive.

A few days later when merging onto the highway, same scenario, temperature shot up to red, flashed a few times then quickly dropped back down to halfway. This time I could smell "burnt water", the temperature gauge went back up to3/4 of the way a few more times and would shoot back down. After arriving at destination, turning car off, the fan stayed on for 10 minutes.

Long story short, took into dealership and was told the thermostat was not functioning properly and needed to be replaced. Warranty covered replacement, and due to the car shortage I was issued a dirty Nissan Versa as a loaner (very annoying to drive after driving a Mercedes for 6 months).

Kind of feels like this could be a trend in other Mercedes since they have a history of similar issues in older models. And, very concerning for a 2020 Mercedes with such low mileage. I've owned a cheap Ford Taurus and Dodge Avenger well over 100,000 miles that were garbage but never overheated. Hope this doesn't lead to other parts associated with the thermostat failing.