THeir is not an API approved synthetic on planet eart that will harm your seals. Seals are damaged by dry rott. It is usualy associated with poor maintence with dino oils or dirty environment. Varnish and sludge build up from over extended oil change intervals with dino and this allows the seal to dry out and crack. This almost never happens to an engine running synthetic it's whole life. So if the seals are weeping they have already been damaged from whatever oil and oil change interval they have been under. I would fix the seals if I thought it was going to be a problem.