I like the nice hot engine & drain out the bottom method, at least once in a while, but I do also use a vacuum extractor. Mine is a Pela, like this
https://www.mailspeedmarine.com/oil-ext ... Gwod1o8AUg It was bought for use on my boat engine as there is no way to drain from the bottom, the Perkins sits right down in the bilge, with bulkheads all round & the sump is only just off the bottom of the hull. This is the case with many boats, so they have always had their oil changed by suction through the dip stick hole, & I have to say that those I have pulled apart, diesel or petrol, have had no more sludge in them than a similar engine that has had it's oil changed in the traditional manner. I think it's important to make sure you are getting right to the bottom, & like chancer, I use a length of copper tube to assist in this. You do have to be a bit careful not to get the engine oil too hot, or the plastic receiver can go very soft & implode on it's self, Yes, I found that out the hard way
But they are a good clean, no fuss way of draining your oil. I keep looking at these,
http://www.ebay.co.uk/itm/121575316624? ... 1436.l2649 & wondering if it would make life even easier. I like the idea that you could just pump the old oil straight into the container that you are going to dispose of it in, no decanting from extractor to a can.
Tim