Even with the hot climate my X is subjected to run in (TX and FL) I use the Mobil [1] 0-40 European Car oil. Iv'e seen the OBC outside temp showing over 120 deg F while towing a 6k lb trailer in stop and go hwy construction traffic many times (AC on Max too). With over 160k miles everything is OK (even OE timing chain guides). Can't understand those who run higher weight oils in these engines.

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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!