THE PREFILTER Before the oil can be put in the tank, it needs to be filtered. Oil filters are readily available. In fact I can use the oil filters from my car, when I change my oil. So they are basically free. The tank I found has the exit on the bottom. You can see the hose coming off the bottom of the tank, going into the first filter, which is usually the cheapest filter I can find or a used one. It then flows out of the first filter into a high quality wix brand oil filter, then through the black hose into a container. Wix oil filters for a VW diesel, filter down to 25 microns. This is about as low as I can go without haveing to heat the oil. The heated wix brand VW diesel fuel filter on the car, goes down to 10 microns. The following picture is only supposed to take up 50% of the page. For some reason it takes up more. So you'll need to scroll to the right to read the text. Sorry maybe bigstep will fix their pagemaker. The oil filter mount on a VW comes off the engine block with three bolts. I bolted the filter mounts onto a piece of 5/16" steel plate. The switch is an oil pressure switch from a chevy. (Get it? When the oil pressure is low, in your car, the dummy light comes on.) It operates a relay that turns the air compressor on until the pressure reaches above 10 psi. which seems to be plenty. Some of the benefits of useing compressed air to push the oil through the prefilter are, that no expensive pumps are needed and compressed air is easy to find or make.