Actually that is a minor weakness in the design. I generally pump about 20-30 times and then let it work. Come back later and the vacuum is gone and about half the oil is drawn out of the pan and into the topsider. Empty the topsider, put the cap on and pump another 20-30 times. It takes 2-3 reps of this, but I always add another cycle after getting the gurgling noises off of the bottom of the pan. Never had a problem with spillage.

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...Tracy

'00 ML320 "Casper"
'92 400E "Stella"