I have had my jack slowly lower my car to the ground overnight. I know they bleed down. If it's all the way up it holds better. I would never even slip my arm under a car on a hydraulic jack. I at least put a jacvk stand or two under a solid spot, even if I don't lower the chassis onto it. Sometimes I lower the car onto the jack stands with some force but not completely.

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Steve
1985 Mercedes 500SL Euro (Gray market)
1995 BMW 520i Euro (Gray market)
1992 BMW 525it Wagon
1994 Honda Del Sol Si