Put new bushes in the freezer prior to installing them so they shrink a bit and warm the subframe again after removing the old bushes. If you use any lubricant be sure it's water soluble. The connection between bushing and subframe is supposed to be solid soon after installation so any permanent petroleum based lubricant is out of the question.

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E39 530dA -02 M-Sport Messing metallic
E53 X5 3.0dA -06 Sport Stratus grey
E70 X5 40d -12 M-Sport Space grey