Once an oil seal has been fitted in an engine. If the engine is never used will the rubber still harden. My thought are yes as most polymers age harden over time, i realise uv light will not come into play once fitted. Your thoughts would be appreciated
An oddity of oil seals is their need for lubrication because they utilise a tiny film of oil between shaft and seal to prevent the seal burring and tearing. Age hardening can be less of a problem than the damage caused to a seal that has dried out. We used to use it (along with ‘suspension wind up’) as an excuse to bounce 6 wheeler Stalwarts over rough ground. Idleness, as with hydraulics, was the enemy of good functioning.
I would say it completely down to the seal material they use various combinations of both material and ways of providing tension to the knife edge of the seal for example i have seen 60 year old seals that are fine yet others that have been fitted to a damaged shaft that you couldn't see with the naked eye fail in a few hours, a lot of crankcase seals simply fail because of pressurization for the wrong side, some of my Trident seals are 40 years old but are still fine.
