Sounds like a pretty good answer, above.

My comment is just that is you are focusing on the self-levelling just for towing, that you are maybe over-analyzing it. BMW doesn't require self-levelling suspension to tow to the maximum tow rating. If you want it, fine, but that shouldn't be driven by a belief that it is necessary for towing. And I sure wouldn't pay thousands for it as part of adaptive drive (if I didn't otherwise want adaptive drive) or pay to purchase a third-row seat that compromises the utility of the vehicle (IMO).

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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