Those bi-metal temp gauges can be way off, mainly because it's in the lid and not at the food level. You could take it out and do an ice bath test and a boiling water test and see if it's functioning properly. I added a tel-tru to my OTS. I generally only rely on it tell give me ballpark where the grill is at temp-wise. If I need to be super accurate I use a digital probe at the grate. That happens almost never, though. The weber ones I find are ok but can tend to go out after a couple of years. Mine would get stuck at 150 and barely move.