I made a funnel that threads into the filler neck on an EJ25 engine (MY 1998-2002, may fit other years as well). Threading is a loose M42xP4.5, so check your vehicle to see if it matches.
This should make oil changes easier and cleaner.
Also, I'd like to note that an oil resistant filament should be used. Anything that breaks down into the oil will be passed into your engine, so confirm your material choice before use! I will not be held responsible for any negligence!
Reduced size of funnel. The larger size was kind of unnecessary. Also, I tightened up the threads. Will print tomorrow and report if new design fits.
Had some printer trouble so I didn't get this done until now... But the print works great! Printed it with no scale adjustment and it threaded perfectly onto the oil filler neck! I need to get the stringing cleaned up, but otherwise it printed and works great!