From what I have heard its mostly based on your car credit and past car accounts, I have no idea what my score is but I never worried about it even when I purchased my Z4 and I was 20

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The Present:
2014 Audi Q5 TDI Prestige
The Past:
2013 Lexus GS350
2013 VW Golf TDI
2007 BMW X5 4.8i LOADED & Loved
2009 VW Jetta
2008 VW Touareg VR6
2005 BMW X5 3.0i
2005 BMW Z4 3.0i
2004 BMW X5 3.0i
2003 BMW 325i
2000 Ford Explorer Eddie Bauer 4x4