I have 7 Noctua fans 4 years old now and 2 had the oil issue that went away after about a week,
Noctua said they had a issue at the factory where to much oil was applied and that it would go away
which it did. I also run a Noctua cpu cooler, I won't use any other brand.
I did have 1 fan (no oil leak) that I had to help it start up with my finger and Noctua sent me a new one
and had me break a fan blade off the failed one and send a pic with my i.d. in the pic, before that...