Now thats a funnel that fits! Its so nice to have a 3D Printer! This is now on thingiverse!
Awesome idea.
I wonder how much commonality there is between engine manufacturers in terms of oil fill caps, or would this need to be custom for each engine…
Well its to much of a difference i believe 
my father had an Vw and this wont even fit a bit but in vw group cars such as audi, skoda, seat they would fit in certain vintages. But this funnel may just fit in M54 motors MAYBE. But not the older or the newer ones i believe.
Have you tried it with oil? If it fits very tight, it may “burp” a lot - a standard funnel let’s air escape around the outside. I like the idea, it just might need the addition of a vent.
I have a piece of coned A4 paper that I’ve been using for more than 3 years. It replaced the older paper cone and it works great on M54
@Alan_Thomason pull out the oilindicator