Sorry if this has been covered but I tried to search for it but found nothing.
Why is the factory oil 5w30 but on the mini owners lounge site suitable alternatives eg Mobil 1 0w40?? Aren't viscosity standards industry standards??

 

Because the actual viscosity lies along a continuum. Then what MINI recommends for oil is a range as well, which overlaps those ranges.

 

It is fine....there is a "range" due to worldwide availability and how engines are machined....some things are not exact....some 5 weights are a bit thicker... Some thinner...even the SAE spec has wiggle room. I would not worry....it is like asking if you have 110 or 120 volt service and if your stove/has 220/240 and some building have 208....but it is refered to as 220....
Very popular oil to use actually....and good stuff!!
Various explanions have been told....but euro mini's list that oil weight as fine....just not common in the us, so I guess it did not make it into our handbook/manual. It is just not worth "non engineer types stressing over....a thousand folks who know nothing more about oil will weight in...
If you are more interested in oil...." Bobstheoilguy.com" website....or very close to it is the place to go...Google it...it is an all oil info site...

 

The short answer is: All of the weights they list are acceptable, and all will be just fine in your engine.

 

Also, the Mobil1 0w40 is the only commonly available Mobil1 grade that meets the wear standards that BMW has set, that is why they label it as 'european formula'.

No worries using the Mobil1 0w40, also some dealers are pretty reasonable with the factory oil prices, as another option.

Have fun,
Mike