I did a little experiment that i though i would share with you guys if your interested......
Well a while back (2 months)my girls father changed a waterpump and the one he changed was still laying around, so i was checking out the o-rings and noticed how dry and brittle they were...i tried to take em off without breaking them, well the first one i took off was so brittle and dry it broke immediately...so i was more careful with the second one and got it off with out breaking it...so in playing around i noticed that if i tried to bend them they would break easily, without even bending them sharply....so with nothing to do at that moment i took some castrol gtx high milage oil (synth mix) off his shelf and put about a quarter of an inch in the bottom of a cup and put the o-rings in it.....
I totally forgot about it for about a week ,when i remembered ,i wanted to see what effect (if any) the high milage oil would have on the o-rings....so i took the o-rings out of the oil and i could not believe the difference in the flexibility and all around strength of the rings compared to when i put them in it...now i dont know if it was just oil that did it, or does the high milage oil really condition the rings that good? i mean i could bend them clean in half and they would not break anymore.....
id like to hear you guys's take on this...cuz if the high milage oils really help the o-rings this much i think im gonna throw at least 2 quarts of high milage oil in every change!!

any thoughts?
sorry if you think this was a stupid idea(post)

 

Any oil will soften or even break down rubber components.

 

Ya, thats what i figured.....i wouldnt think that oil intended for automobiles would actually break down the rubber they use for the orings....i guess if it did cars would b e springing leaks all over the place!

 

Depends on the "rubber". Neoprene and silicone o-rings, no. Rubber tires, motor mounts, brake lines yes. HM oils are supposed to soften and swell seals and oring gakets.