I've heard of some horror stories of deteriorating on higher mileage on M62s. My friend had a 97 540i with the M62B44 that needed timing chain guides after about 160,000 miles. His was very unusual because the inside of his motor was very clean and looked to be well maintained. The only other times I've heard of it being a real issue is when the motors are abused and not maintained properly. We had a 740il with the same engine and never experienced any guide problems. Given my X5 has the N62B44 I really can't comment on prone it is to guide failure. We had a 745i and now a 645ci with the same motor but they were not at that high a mileage.

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2004 BMW X5 4.4i-Sports Package-Premium-140,000 Miles