The only practical way is to replace the seals. They are fairly expensive but are easy enough to replace. The long molecular strings in the rubber have broken so are no longer as elastic as when new, and nothing will join them back together.
Silicone won't hurt, and neither will Armor All, but don't use WD-40 on rubber. It is a mixture of petroleum distillates that will speed the breakdown of the rubber. Don't drink it either - the MSDS warns "Harmful or fatal if swallowed. Combustible Liquid. If swallowed, may be aspirated and cause lung damage." WD-40 is good for the inside of distributor caps but not much else, and is absolute death on locks after a year or two.
www.wd40company.com
How do I make the rubber seals around doors look new again?
Linear Mode
