Most oil objectives used on inverted microscopes require the solution to
two obvious problems.  The use of something to soak up extra oil like
sponges cut with holes or services attached with rubber bands is a good
way to minimize oil running down the sides of the objectives & into the
nosepiece.
The other thing you want to do is prevent oil from getting between the
shell and the spring load mechanism by "sealing the objective". The Nikon
repair dept has silicone rubber caps for the CF 60x Apo oil and now the
CF plan Achro 50x oil objectives - contact Bob Grimm at 516-857-7788 /
[log in to unmask]

I have a couple of procedures for sealing objectives I could fax you with
diagrams. Email me your fax address [log in to unmask]

Mel Brenner
Nikon Biomed dept.