Orics. Thats what I did with my Bimmer.
I ran 5w40 BC this summer and then I switched
to GC in November a few weeks before I put the
car in storage. I don't know what I'm going to
do next summer though. I have a stash of 24
bottles of the green GC which will last me
another four years. I only put about 7000 km
(4200 mi) per year in my BMW so I only change
once a year. Doing your OCI at 7500 mi or 6
months is best. Do not go the full 15000 mi.
PS. Orics, what grade does your owners manual
recommend? My manual for my 2000 328i recommends
5w30 but I can use any xW30/40/50 grade with x
being 0 or 5 weight and also 10W30/40/50 oils
in the summer months.