As far as O-ring lube: what you will typically find is that the majority of O-rings are made of "Buna-N" rubber. This is the most cost-effective material by a pretty fair margin, with the happy combination that this material also has good abrasion and wear resistance, and very good resistance to petroleum products.
If you were to go into a random hardware store to purchase O-rings, the chances are extremely good that you'd walk out with Buna-N if you were not given a choice. There's just THAT many Buna-N O-rings in the world.
Buna-N has a weakness, which is ozone. Ozone is present in the atmosphere in minute quantities, and in heavier concentrations around electic motors where it gets formed by the arcing of the brushes. Ozone will attach Buna-N over time and cause it to crack, especially true on O-rings that are under tension (stretched over something). But if they are protected from Ozone, like in a flashlight where they are lubed and covered up, they will be fine.
We prefer Neoprene O-rings, which cost more but have all the same good properties of Buna-N plus they are better with Ozone.
There are a couple types of O-ring material that will be attacked by petroleum (Vaseline etc), but they are specialty O-rings usually only found in very specific applications. Relatively rare and expensive.
Like someone mentioned, Mag specifically recommends Vaseline. That tells me Mag is using Buna-N or maybe Neoprene, as they are both excellently suited for the task AND quite inexpensive.
A silicone-based grease is very inert as someone mentioned, and is not a bad choice either.
