Mine is a 2002 3.0 diesel (I live in Europe) with 251 000 km on the clock. Normal endemic X5 issues (suspension arms & bushings, final stage resistor) but original diff's, water pump & engine. My transmission is fine (5 speed manual) and NV125 transfer case, but I've proactively changed oil on EVERYTHING, even the "lifetime" oil. I've also added magnetic drain plugs everywhere, as BMW no longer puts them on manual transmissions and didn't on the transfer case. There is an improved PCV for the diesel engines, a better part and not as much an issue as the 6 cylinder or V-8 gasoline engines. My mileage is around 8 L / 100 km (combination of city & highway), goes to 7 L or better on highway only.

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2002 Euro X5 (E53) 3.0 diesel (M57)
5 speed manual with UUC short shifter.
Pre-xDrive NV125 transfer case (chain & gears).
Factory Xenon headlights, Spyder LED tail lights
Updated vortex crankcase breather.
Motorsport dead pedal, factory fire extinguisher, factory first aid kit, factory F&R mud flaps, factory PDC

Bilstein B6 shocks F&R
Redline oil has replaced "lifetime" fluids (F&R diff, manual transmission, transfer case and P/S).
Dimple magnetic drain plugs in all compartments.