LIQUI MOLY Hydro-Stossel-Additiv is a multifunctional engine oil additive that prevents and eliminates the knock of hydraulic valve lifters. Eliminates the causes that cause the knock of hydraulic lifters. The special formula allows the additive to clean the thinnest oil system channels available in gas distribution systems and improve the lubricating properties of engine oil. Thanks to this, the hydraulic lifters begin to lubricate normally and the noise from their work will disappear.