Gents FYI, One huge reason why these GM-sourced magnetorheological shocks leak is due to lack of use! It's quite a long, drawn out explanation given the morphology of rubber elastomer seals. Basically, all types of rubber seals naturally outgas (or release its gaseous components into the atmosphere) and are prone to getting an unwanted permanent set after time, especially if not "wetted" by fluid during use. The wetting provides some lubrication and may also induce a bit of swelling to ensure full contact on the sliding surfaces. As-machined surface finish of the sliding surfaces can also be a factor for long term sealing reliability. Remember the rainbow colors found on the inner windshield surfaces after exposure to hot sun or UV light, those are the gaseous elements that outgas from the leather or vinyl dashboards, especially after application of some type of treatment like Armorall (really bad!) and causes the dashboard materials to dry out and subsequently crack prematurely. Ultimately, any grease lubricant that's been applied (if any) during component shock assembly also dissipates given time, temperature and ambient conditions. Then there's also the dreaded external contaminants, eg, fine dust, chemicals, etc., that the rubber seals could be exposed to while driving on the road; those may either damage and/or dry out the rubber. More so, I believe GM's former Delphi division invented and designed these type of magnetorheological shocks circa late 80's or early 90's and believe it or not, rubber elastomer science was not the same as 10 years later when newer, more robust, resistant to wear and less contaminant-sensitive types of rubber and seal designs were invented. Around the early 90's, I had worked with a consultant rubber scientist to analyze certain rubber compounds that were resistant to low-earth-orbit space conditions for use in the Japanese module Kibo and NASA for the Space Station. Even he called rubber science a "black art" at that time!