PS I forgot to mention earlier, but as another poster noted, THOSE FELT WASHERS WORK GREAT..If you use BOTH them AND the red or yellow regular cover/sealer anti corrosive spray designed specifically for battery connections YOU LIKE NEVERRRRRRRRRRR HAVE TROUBLE.
As an enginner I must again recommend you DO NOT cover them with regular petroleum grease (NOT a good electrical conductor, a dielectric even) which can possibly flow down and get between the post and terminals. Lead to lead is a better conenction then lead to grease to lead YUKKKKKKKK Sure grease can work as its reduces oxygen and moisture contact but since its NOT a good conductor and could get between the post and connector, the regular spray coating/sealer is so much better electrically speaking. Grease a dielectric especially the electronic dielectric grease is great in the proper application as it doesnt conduct and cause a short but its NOT good to have it in the electrical current path (Lead to grease to lead), its an insulator NOT a conductor remember
Your money your choice, do what yall like
God Bless and Merry CHRISTmas