Haven't seen the X-Drive invite, but I got asked to participate in the 750 event. They gave the cars out for a full day or more, and kept your own vehicle and detailed it for you. Not sure what I bought or said to get asked along. I ended up out of the country that week and missed it, but would do it if asked again.

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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