On my 35d,I have to drive for about 20 miles at operating temperature to see a change in the oil level. Fortunately, the engine also has an actual dipstick so I don't have to wait.

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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