You probably have a leaking oil seal or cylinder head gasket.
If it is a CVT transmission then yes you can use cvt gearbox oil in a mini cooper.
Use exactly the weight that Mini recommends. http://www.ehow.com/list_7739452_list-mini-cooper-approved-oil.html
The manufacturer recommends that you use 10W-30 motor oil in your 2006 Mini Cooper. Use in extreme climates may call for a heavier oil, like 10 W40.
yes, i use royal purple.
Use exactly what the manufacture recommends and nothing else.
Consult your owner's manual.
Wrong oil filter. Must use OEM oil filter in Mini's. The aftermarket filters dont have the proper check valve inside.
I use about 4.25 qt (about 4 L)
The 2008 MINI Cooper runs on premium unleaded (required).
The 2002 MINI Cooper runs on premium unleaded (required).
The 2007 MINI Cooper runs on premium unleaded (required).
The 2012 MINI Cooper runs on premium unleaded (required).