I was told you cant just regue the tires because the old glue wont let it bond right. Do a search for reusing tires or rims and they will tell you how to get them off so you can put them back on clean. From what I read you could either boil them or use nail polish remover but look it up first.

For the diff oil I think adding silicone wouldnt let the wheels balloon as much which wouldnt cause the tires to pull from the rim. (Its just a guess)