My wife wanted butterflies on her valve caps so here we are. I wouldn't recommend this for a car as it might just get flung off at high speeds. Print it laying flat and no supports. I printed with a 0.4mm nozzle and it came out good enough, but you really need a 0.2mm nozzle to capture all the detail. Try adjusting your line widths or toggling "detect thin walls" to get as much detail as possible.

Prusa

i3 MK3

No

No

0.2

15%

0.2mm nozzle would be better. If your flow rate is on point the threads should fit just right with minimal cleanup needed.