Is it hot in here or should I change my thermostat?
The thermostat in your BMW is just one component that is part of the cooling system. Upon inspection of your cooling system, or at the time a hose,(s) are changed, or even a cooling flush, it may be recommended that your thermostat be replaced, also. The thermostat should be replaced by age/time. They eventually wear out and whether they “stick”closed,(causing overheating), or stick “open” or partially open, you have a marginal situation that will only get worse. So, in other words, it may appear to you, that it is “OK”, because your car did not overheat. But, if it is not operating properly, one of the results is increased fuel consumption. Your engine does not get to the proper temperature, and because it takes longer to reach optimum temp, it is now using more fuel.
They are pretty neat little units, and you might want to take a look atone after it has been removed for replacement. It may be easier to understand their operation and the need for replacement when you examine a new thermostat vs. an old thermostat. Your BMW and MINI professional should be happy to “show and tell”.