This is an old trick - I didn't invent it. But I got tired of dribbling a little oil down the engine when I added a quart. I now use this system - it fits the oil fill hole perfectly. I still put a towel there "in case" but I have never spilled a drop using this. After you've poured in most of the oil you can invert the bottle and it will rest in this funnel to completely drain without falling over (unless you're in a stiff cross-wind, i guess.)
And its free! Note you can store the funnel in the remainder of the old bottle so the last of the oil drains out of it, and you can use the cap to keep it from dripping as well.
