I own and use an electric vacuum pump, I did a service on my own car last week, oil and filters etc.
Today I dipped my oil to check it was up to the full mark on the dipstick, the oil is still clean.
Incidently after I have drained the oil, upon removal of the oil filter, the oil in the filter canister is all there is left in the sump.
When using the vacuum pump it is worth pushing the tube hard down through the dipstick tube until it stops dead that will ensure the tube is all the way to the bottom of the sump.
It is also a good idea to go for a drive around the block in order to get the oil hot and also to ensure the oil is well agitated prior to using the pump.
This is the pump that I own,
http://www.ebay.co.uk/itm/Electric-O...item27c890b003