X5's are money pits, no way around it. Even the best kept example of one will still have issues that spring up, obviously less than one that's neglected. Doing the work yourself will save you some coin but don't think you can just change some fluids and it will have the reliability of a honda. With all of that said though, I'd rather have to spend the cash to have the enjoyment of driving. I have a honda and the thing sucks. As a commuter car does fine, but every time I get in I cringe. It's a soul less piece of machinery.

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Current garage:
'03 4.6is Proud X5 Peasant
'93 Jeep Cherokee (XJ)
'07 Jeep Liberty (KJ)
'88 Jeep Comanche (MJ)