The prior owner had the dealer do changes according to the SII (Service Interval Indicator), so the X had BMW oil approx every 15k miles for the first 100k miles. I switched to the Mobil [1] 0-40 EuroCar oil when I bought it and I change it when the SII has 2 green bars still lit, around 7k miles on the oil.

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'03 X5 4.4 Sport, last of the M62s (8-03 build date)
I believe in deadication to craftmanship in a world of mediocrity!