For the last couple of years I have used walmart batteries in my bmw's. I had used autozone duralast batteries before that. The biggest problem with either the duralast or the walmart ones seems to be if you ever let them drain down to far. That shortens any batteries lifespan but it really bothers the duralast or the walmart ones. The factory battery didn't seem to be effected as much.

My x5 has a interstate mega-tron or something like that in it now. Its pretty weak but I think it has been abused by the previous owner and I have had it run down twice from the Bluetooth module.

My next battery will be a deka intimidator. Seems to be the best out there from my research.

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Just BMW's - All cars and trucks was two pages long
1994 318is
1997 528i
2000 323i
2001 X5 3.0 auto
2005 X5 3.0 auto
2011 535xi auto
2013 X5 xdrive35 Turbo
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