Prepared additives for mineral oils are classifiable under the specific tariff heading, not a general petroleum oil heading.

An engine oil saver was treated as a prepared additive for mineral oils because its composition and product literature showed anti-knock and viscosity-improving functions. Heading 38.11, which specifically covers anti-knock preparations, oxidation inhibitors, gum inhibitors, viscosity improvers and other prepared additives, prevailed over Heading 27.10, which applies to petroleum oils and preparations containing 70% or more petroleum oil but excludes prepared additives. On that basis, the product was classifiable under Heading 38.11 and not under Heading 27.10, and the assessee's classification was upheld.

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Issues: Whether the product known as oil saver of engine was classifiable under Heading 27.10 as a petroleum oil preparation containing 70% or more petroleum oil, or under Heading 38.11 as an anti-knock preparation or viscosity improver.

Analysis: Heading 27.10 covered petroleum oils and preparations containing by weight 70% or more of petroleum oils, but the heading was subject to the exclusion of prepared additives. Heading 38.11 specifically covered anti-knock preparations, oxidation inhibitors, gum inhibitors, viscosity improvers, and other prepared additives for mineral oils or for other liquids used for the same purpose. The product's composition and literature showed that it functioned as a prepared additive for mineral oils and had anti-knocking and viscosity-improving properties. Since functional use and the specific description in Heading 38.11 were decisive, the product fell within that heading notwithstanding its mineral oil content.

Conclusion: The product was correctly classifiable under Heading 38.11 and not under Heading 27.10; the classification adopted by the assessee was upheld.

Ratio Decidendi: Where a product is a prepared additive for mineral oils and is specifically covered by a more particular tariff heading, it is classified under that specific heading rather than under a general heading based only on predominant mineral oil content.

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