There aren't posts on here about oval cylinder bores, as I recall. What doesn't fit for me is that both the M62 and N62 use the same technology for the cylinder bores (aluminum blocks with Alusil). Not sure why one would be much different than the other.

Deposits on valves are often related to poor quality fuel, with insufficient additives to clean the deposits away.

There are lots of things that can break on an X5, and some maintenance and repairs will be required, but engine overhauls are not one of the things I would be worrying about.

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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