My business partner has a 3D printer. He uses Solidworks to design. I got him to come look at my 911 and how much a pain it is to add oil to the tank, especially for an oil change. You can see the funnel holds onto the stock air intake, and does not move.
He had to struggle to figure out the right angles and make it work. It is designed for my 85 911 3.2 Carrera. The funnel sits in place, and a bottle of oil will just sit in the top all by itself, and drain out without holding the dang bottle.
The tip of the funnel has a screw on cap to keep that end clean, and and just stuff a paper towel in the other end. The funnel stays clean. This is the funnel right off the printer with the supports that snap off when done.
I have been selling them for $35 delivered to your USPS mailing address.