You will never get ALL the oil out. If its doing its job it will be coating the internals of the engine. And are you stating it for a min to fill the oil filter before you call it done? That's 1/4 to half a cup right there. If you really want the insides clean you can run some sea foam cleaning in the oil a few hundred miles before the oil change, that will pull off a lot of the deposits and allow more oil to go in. I would NEVER recommend pumping the oil out the top as you are bound to drip sludge from the bottom up higher in the engine. Always run a pure synthetic, and if you really want to be nice to it pour a quart of new oil through after it drains as a rinse.