Took my grandfather for an Opel. Old German, ate oil and smoked. In addition, there was a leak on the seals, not strong, but annoying. Repairing such an old car is expensive. Therefore, I tried the German additive. In general, the smoke disappeared, the leak on two seals was gone, on the third it decreased, to not terrible. The main thing is that all this is safe, and it helps, as it seemed to me quite well for such a price.