I'm more of an Arduino guy, but yes, and that's probably even overkill but nice to have the isolation and for sure the voltage transition since I think the Pi is 3.3v. You should maybe make sure of the voltage that the X5 uses on the CANbus. Is there maybe a sketch to use the Pi as a logic analyzer ??

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)