Lubricating oil composition and method for using lubricating oil composition

A lubricating oil composition with a specific blend of antioxidants for base oils with tertiary carbon atoms addresses oxidation stability and initial acid value issues, achieving prolonged stability and reduced acid rise in high-temperature conditions.

EP4116395B1Active Publication Date: 2026-06-24IDEMITSU KOSAN CO LTD
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Patent Information

Authority / Receiving Office
EP · EP
Patent Type
Patents
Current Assignee / Owner
IDEMITSU KOSAN CO LTD
Filing Date
2021-03-05
Publication Date
2026-06-24

AI Technical Summary

Technical Problem

Lubricating oil compositions containing a certain amount or more of tertiary carbon atoms face challenges in maintaining oxidation stability over a long period and suppressing the initial rise in acid value, as conventional antioxidants are ineffective in these oils, and traditional evaluation methods like RPVOT do not accurately reflect real-world performance.

Method used

A lubricating oil composition comprising a base oil with 8.0% or more tertiary carbon atoms, combined with a specific blend of amine-based, phenol-based, and phosphor-based antioxidants, including diphenylamine, hindered phenol compounds with ester structures, and phosphite antioxidants, within defined content ranges, to enhance oxidation stability and suppress initial acid value rise.

Benefits of technology

The composition maintains excellent oxidation stability over time and suppresses initial acid value increase, ensuring prolonged performance in high-temperature environments.

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Abstract

The task is to provide a lubricating oil composition capable of maintaining oxidation stability over a long period of time by not only making oxidation stability evaluated by an RPVOT value excellent even while using a base oil comprising a certain amount or more of tertiary carbon atom but also suppressing a rise in acid value in the initial stage. Said task is attained by providing a lubricating oil composition comprising a base oil (X) comprising tertiary carbon atom at a content of 8.0 at% or more based on the total carbon of hydrocarbons, and an antioxidant (Y) comprising an amine-based antioxidant (A), a phenol-based antioxidant (B), and a phosphor-based antioxidant (C), and satisfying the following requirements. Specifically, the amine-based antioxidant (A) comprises a diphenylamine compound (A1) having a specific structure. The phenol-based antioxidant (B) comprises a hindered phenol compound (B1) having an ester structure. Furthermore, the total content [(A1) + (B1) + (C)] of the diphenylamine compound (A1), the hindered phenol compound (B1) having an ester structure, and the phosphor-based antioxidant (C) was set to greater than 1.0 mass% and 2.0 mass% or less based on the total amount of the lubricating oil composition.
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