er..... why fit a vacuum cleaner hose to the oil filler, why not just leave the filler cap in place? This will give an airtight seal whereas if you held or even taped a vacuum cleaner hose in place you are bound to get a small air gap. I fear that whatever you do, you will get a flow of oil from the drain plug when you undo it to re-seat it, so just place a pan underneath when you do the work to catch whatever comes out