The manual says to use MINI oil for oil changes, how important is that?

Find out from Mini Dealer, what viscosity the oil is { I think it is 10W30 full synthetic} You can ask if they will send you the correct amount and a filter. If you can change it yourself, do so. Any one of the quick Lube places can change it for you for a fee. Lately I have been using Royal Purple in my Mazda Miata MX5 and it works great.

Depending on where you live- as in do you experience warm summers AND cold winters- the recommended oils are: Winter: Synthetic 5W30 and Summer: Synthetic 10W30 I live in Ontario, close to Toronto, and have occasionally used the services of 'Mr LUBE’ for an oil change and filter and have been favourably impressed overall.The outlet carries MINI designated oil filters ie: the "MINI" name is actually shown via a MINI sticker on the filter.The accompanying wording indicates it is actually the same filter as is used/distributed at BMW/MINI dealers. You could call one of the many lube places to see if they carry such a filter. To the best of my knowledge there is no such thing as a "MINI" branded oil, rather it is, as the previous writer says, the oil viscosity that is relevant.There are, though, certain BRANDS of oil considered better than others and you may well want to select one of these for your Countryman S.