OID vs overall system performances on high load

I am still in the dark due to my lack of knowledge on internal OID management,but
i would presume that a table with OID enable and that has high load would require
some more work from pgsql internal to maintain the OID index for the database.

So OID can be beneficial on static tables, or tables that you want to be able to manipulate
with pgadmin X , but can a table without OID increase performances on insert,delete,update,COPY?

I am not really worried about disk space that an OID collumn can take, but i was wandering if an
insert in a table of 20 millions and more that has oid would slow the insert process. Since OID seem
to act as a global index mabey maintaning that index can become costy over high table load by postgresql
backend.

-Eric Lauzon