GOST 25371-2018 PDF

Full title and description

GOST 25371-2018 — Нефтепродукты. Расчет индекса вязкости по кинематической вязкости (Petroleum products. Calculation of viscosity index by kinematic viscosity). The standard specifies calculation methods for the viscosity index (VI) of petroleum products based on kinematic viscosity measurements, and updates the previous GOST 25371-97 system to use kinematic viscosities at 40 °C and 100 °C.

Abstract

GOST 25371-2018 establishes two calculation methods (method A and method B) for determining the viscosity index of petroleum and related products from kinematic viscosity values at 40 °C and 100 °C. Method A applies for VI from 0 to 100 inclusive; method B applies for VI ≥ 100. The standard references established procedures for measuring kinematic viscosity and notes equivalence with earlier temperature bases (37.78 °C and 98.89 °C) used in older systems.

General information

• Status: Active / in force (replaced GOST 25371-97).
• Publication date: Adopted May 30, 2018; approved by the Federal Agency for Technical Regulation and Metrology (Rosstandart) by order dated 11 September 2018; introduced as national standard (date of implementation) 1 July 2019.
• Publisher: Interstate (regional) standard published under the auspices of the Inter‑governmental Council on Standardization, Metrology and Certification and introduced as a national standard by the Federal Agency on Technical Regulation and Metrology (Rosstandart).
• ICS / categories: 75.080 (Petroleum products in general).
• Edition / version: 2018 (current edition with later amendments and corrections published as informational updates and a formal change entry).
• Number of pages: Published versions vary by distributor (typical Russian-language editions range around 16–18 pages depending on publisher/format).

Scope

This standard applies to petroleum products and related liquids for which a viscosity index is required. It specifies two calculation procedures to compute the viscosity index from kinematic viscosity measured (or converted to) 40 °C and 100 °C. It is intended for use when kinematic viscosities at these two temperatures are available; where they are not, the standard allows estimated conversions from measurements at other temperatures for information purposes only, not for conformance assessment.

Key topics and requirements

• Definition and calculation of viscosity index (VI) from kinematic viscosity at 40 °C and 100 °C using two normative methods (Method A for VI 0–100; Method B for VI ≥ 100).
• Specification of units and practical use of centistokes (cSt, mm²/s) for kinematic viscosity.
• Reference to accepted test methods for kinematic viscosity determination (GOST 33 and GOST 33768 or their equivalents).
• Guidance on converting viscosities measured at other temperatures into values at 40 °C and 100 °C for informational estimates (but not for official conformity tests).
• Requirements for result processing, reporting (test protocol), and stated precision/uncertainty provisions for the calculation procedure.
• Notation of amendments and corrections published after original adoption (informational indexes and a formal change entry).

Typical use and users

Used by petroleum refiners, lubricant and fuel producers, quality control and testing laboratories, standards bodies, certification agencies and regulators for product specification, QC reporting, acceptance testing and formulation evaluation where viscosity characteristics are critical (e.g., lubricants, engine oils, fuel oils, hydraulic fluids). The standard is applied in both production QA/QC and third‑party test laboratories.

Related standards

Normative references and related documents include GOST 33 (determination of kinematic and dynamic viscosity), GOST 33768 (method for determination of kinematic viscosity and calculation of dynamic viscosity), and the international standard ISO 2909 (Petroleum products — Calculation of viscosity index from kinematic viscosity), which the 2018 text takes into account. The standard sits within the MTC 31 family of petroleum fuel and lubricant standards.

Keywords

viscosity index; viscosity index calculation; kinematic viscosity; centistokes (cSt, mm²/s); petroleum products; lubricants; GOST 25371; ISO 2909. (Russian keywords: индекс вязкости; кинематическая вязкость; нефтепродукты).

FAQ

Q: What is this standard?

A: GOST 25371-2018 is the interstate (GOST) standard that defines how to calculate the viscosity index (VI) of petroleum products using kinematic viscosity values at 40 °C and 100 °C; it replaces the earlier GOST 25371-97.

Q: What does it cover?

A: It covers two calculation methods for VI (Method A for VI 0–100; Method B for VI ≥ 100), units and practical conventions (centistokes/mm²/s), reference measurement methods for kinematic viscosity, result processing and reporting, and guidance on estimated conversions from other temperatures for informational use.

Q: Who typically uses it?

A: Refinery technologists, lubricant formulators, QC and test laboratories, standards organizations, certification bodies and regulators involved in petroleum product specification, acceptance testing and research use the standard.

Q: Is it current or superseded?

A: It is the current (2018) edition and supersedes GOST 25371-97. The 2018 edition has had informational updates and at least one formal change entry published after adoption; users should verify they have the latest consolidated text and amendments before relying on it for conformity decisions.

Q: Is it part of a series?

A: Yes — it is part of the petroleum and lubricants standards developed under the Inter‑governmental technical committee MTC 31 and is classified under ICS 75.080; it references and aligns with ISO 2909 where applicable.

Q: What are the key keywords?

A: Viscosity index, kinematic viscosity, centistokes (cSt / mm²/s), petroleum products, lubricant testing, VI calculation.