Originally Posted by
easyupbug
Greases are made to very slightly expand most all o-rings materials for improved fit and service life but not repair a worn o-ring, if you use them periodically your o-rings will last much longer.
Lubricant will reduce friction and, thus, wear on the o-ring but no lubricant should change the characteristics of an o-ring. Having swollen many o-rings because of chemical incompatibility, I can tell you that a swollen o-ring is not something you want.
Any change to the physical characteristics of the o-ring from swelling to softening to hardening will result in improper performance of the o-ring. The result may be only a slight decrease in performance or it could be disastrous.