I used royal purple in mine and have had no issues. No special fluid needed. The BMW oem fluid works just fine too, but not at $ 150.00. lol I think he may be taking advantage of you. Have you had the work done already? If so ask him to show you the bottle he used.

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2010 X5M /// R63 AMG...Wifey's 540HP Family Hualer

2001 X5 3.0i Sport 335,448 miles & counting...
SMG M3 Steering wheel
E46 Stainless Racing Headers
4.6is Exhaust
Turner Pulleys
Afe Intake
Brembo drilled rotors
PowerFlex Bushings
Hualingan
30mm H&R Spacers rear
20mm H&R Spacers front
Bavarian Autosport High-Performance Coils
Active Autowerke's Performance Software