Those short trips will do it, if you don't get it out for a longer drive on the weekend.

The engine cleaners can be harsh on engine internals, seals and so on. That is why BMW doesn't recommend using them. I would just do a couple of hot oil changes a week apart, and get it good and hot in between. Realize that the vent system isn't in an oil circulation circuit, so something you add to the sump doesn't necesarily get into the crankcase vent system.

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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