My post below wasn't intended to cause trouble but to prevent it. Sure not trying to get folks excited!
A lot of people only read forums occasionally instead of posting questions and may not have much if any experience on the subjects. That sometimes results in blindly following advice that quickly or slowly causes serious grief. With airguns being as difficult as they are to take apart and reassemble correctly, especially for beginners, we don't want folks screwing up the works based on bad advice they got here.
The only correct answer to the question of lube or pre-assembly lube is to use what's best for a particular gun. That depends on what the seals and gun parts are made of, so it's a matter of finding that out, if posssible. Petroleum based seals should not use petroleum based lube. Silicone based seals should not use silicone lube. Petroleum based lube can attack certain plastics, but not all plastics: so a person needs to know exactly which plastics [if any] are used. Each person needs to educate themselves on their own particular airgun's components and materials.
Bottom line is, just because one person gets away with using a particular lube in their airguns, maybe even for years and years, that doesn't mean that it applies to every airgun in every situation.