A word of warning about using products that sink into the wood by adding oil or other substances. They break down the adhesion between the teak and ‘black stuff’. Water then gets in the crack and under the wood. I used to own a boat that the previous owner of 15 years had regularly added Teak Wonder. The top surface looked quite good but the underside of the wood was black, wet & rotten. Bavaria specifically state that you should not use these products and they are right. Either clean it, leave it or seal it and the latter needs regular maintenance of the seal.