Yes, the fuel mileage is superb for such a vehicle and its drivetrain. Love mine. I'd look at the front sway bar end-links. Could be the sway bar bushings also.

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8/2011 X5 xDrive35d Sport, Black Sapphire Metallic, Black Nevada Leather, Fine Burr Walnut Trim
2/2001 M5, Jet Black, Exclusive Complete Black Walk Nappa Point Heritage Leather, Black Cubic Trim