I look more closely at the lift height than the tonnage; 18.5" is probably ok for an e53, but higher is better. I bought a floor jack at Sears several years ago with a 22.5" lift. I'm a big guy and appreciate the extra few inches.

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2001 X5 Sport 3.0/5-speed
1998 318ti/5-speed
1988 735i/5-speed
1984 528e/5-speed (soon to be M20B25-powered 525i!)