If you go to an aquarium shop you will find the tube the goes down the dipstick, and it fits inside the pumps pipe.How are you draining it?
Sump nut out will probably get more out than pumping through the dipstick tube. For a full drain you also need to drop the oil cooler hoses.
My sump nut is so totally 'd that I have to use a pump via the oil cooler fitting on the sump. That has the benefit of also getting pretty much all the oil out of the cooler, but not as thorough as dropping all the hoses. I bought 7L but only used 6.
Before anyone asks, both the tube supplied with the pump and the narrower one I bought are too wide for the dipstick tube:furious:
Not every oil change but every car I've had I've put it in at the first oil/oil filter change. It goes back to the '80s and an advert I saw where they ran 3 cars round a circuit for 10 minutes or so to get them hot, brought them in, changed the oil on all three and put Slick 50 in one (Strada I think) sent them out for 30 minutes, brought them in, dropped the oil out of all and sent them out again. Strada kept going but the other two didn't last a lap!Do you always use Slick 50?