I wouldn't do an extra oil change in the spring.

I would just use a general petroleum-based solvent/parts cleaner. I suspect the throttle body cleaner has something stronger in it.

Your short warm routine sounds just right. The 10 km drive is the problem. That will take 15 minutes or so, so the vehicle never gets and stays hot. You need to get out and drive for an hour regularly. It is the time spent at full operating temperature that burns off the moisture. If you can't drive it longer than 10 km at a time, then you should plan to service the CCV annually IMO.

Sitting for the winter doesn't hurt it if that is what makes the most sense for you. It is the constant warming and cooling cycles caused by short trips that causes it, not the cold itself.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue