I bought a 2000 Bonneville SSEI back in April. It only had 18K miles on it, but I've already put on 6K miles and am going to be getting the oil changed and tires rotated soon. I've been wondering about the supercharger oil and read posts on here that said it should be changed every two years or 55K miles. Because I'm not sure about the maintenace history before I bought my car I figure I'll just take care of it now to be on the safe side. So, my question is - Do I have to change the supercharger oil or just fill it if it'* low? If I do change it now what would a good schedule be after that? Thanks!

Because it is easy to do and inexpensive I change mine once a year.
Great article in teck info on how its done.

If you are running more boost than stock, then I'd say once a year is a good way to go. The */C spins faster so extra care is required. Every two years should be fine on unmodified cars. The stuff lasts a long time.

It only needs to be filled up to the threads on the cap on the snout.

You can go ahead and change it now though. It wouldn't hurt.