We bought our last two new BMWs the same day, the 535 and the X3. Traded the X5 and the Z4, and sold the 325xi privately. Dealer offered to take all three on the two new vehicles, but I could do better on Craigslist with the 325xi; he did much better on the X5 than I could do privately, and while he just did OK on an offer for the Z4, I didn't want joyriders coming around so I took the deal.

You won't necessarily do a lot better, but as noted above, it can't hurt.

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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