For starters, the compressor should barely need to run for normal driving. Are your rear air bags leaking? Does it look like the rear end is squatting in the morning?

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'08 X5 4.8i - 190k
'15 i3 - 95k - Blown AC compressor

'98 323is - 170k - Garaged
'94 325i - 208k - Sold