HSN Code 3811 refers to "Anti-knock preparations, oxidation inhibitors, gum inhibitors, viscosity improvers, anti-corrosive preparations and other prepared additives, for mineral oils, incl. gasoline, or for other liquids used for the same purposes as mineral oils." This classification code is essential for identifying chemical additives used in the petroleum industry for import/export purposes based on their nature, composition, and intended use. Common products under HSN Code 3811 include fuel additives, engine oil additives, and corrosion inhibitors. Additionally, the GST rate for these chemical preparations under this code supports accurate trade compliance.