DIN 51354 Testing of Lubricants - Determination of Shear Stability of Polymer-Containing Lubricating Oils

The standard “DIN 51354 Testing of lubricants – Determination of the shear stability of lubricating oils containing polymers” published by the German Institute for Standardization (DIN) consists of the following subsections published under the same title:

• The standard "DIN 51354-1 Part 1: KRL test method (FZG gear machine)" describes a method for determining the shear stability of polymer-containing lubricating oils. Polymer-containing oils, such as multigrade engine oils and hydraulic fluids, can lose viscosity under mechanical stress due to polymer degradation. The KRL test evaluates the extent to which viscosity decreases under defined conditions.

The KRL test is known as the ball bearing-roller bearing run-in test. These tests utilize a modified FZG gear test rig. During the test, the oil is subjected to high mechanical stress in a roller bearing test rig. After a specified number of cycles, the viscosity loss (usually at 100°C) is measured. The percentage loss of kinematic viscosity is calculated and used to assess the oil's shear stability.

This standard is used for engine oils, hydraulic fluids, and gear oils that improve the viscosity index. This test is particularly important for quality control and product development in lubricant formulations where long-term viscosity retention under mechanical stress is critical.

For organizations working with lubricants or mechanical systems that require consistent performance under load, the DIN 51354-1 standard is one of the fundamental standards for ensuring product reliability.

• The standard "DIN 51354-2 Part 2: Sonic shear test method" describes a sonic shear test method for assessing the mechanical shear stability of polymer-containing lubricants. This standard applies to oils such as multigrade engine oils, hydraulic fluids, and other lubricants containing viscosity index improvers (polymers). It evaluates how polymer molecules are disrupted when subjected to mechanical stress by ultrasonic energy. The results indicate the oil's resistance to viscosity loss under such stress.

These tests utilize a device that uses ultrasonic energy (a sonic shear device). During the test, a sample of the lubricant is exposed to sound energy for a specific period of time. After the test, the kinematic viscosity (usually at 100°C) is measured. Viscosity loss (as a percentage) is calculated. The result represents the shear stability index; the lower the viscosity loss, the more stable the oil is under mechanical stress.

This standard is used in engine oil and hydraulic fluid development, quality control of multigrade oils, and evaluation of viscosity index improvers (VII).

Comparing these two standards yields the following results:

• The type of mechanical stress is roller bearing (FZG gear test fixture) in the KRL test (DIN 51354-1), ultrasonic energy (sonic test) in the sonic sliding test (DIN 51354-2).
• Test duration typically takes hours in the KRL test, shorter (minutes) in the sonic shear test.
• Simulation of the real world is high in the KRL test (gearbox-like conditions), lower in the sonic shear test (idealized laboratory conditions).
• Viscosity loss measurement is possible with both test methods.

The DIN 51354 standard is important because it provides methods for determining the anti-wear properties of lubricants. This standard defines repeatable and standardized test methods for measuring how effectively a lubricant protects sliding surfaces against wear. This standard is considered necessary for the following reasons:

• Consistency and comparability: Without a standard, manufacturers and laboratories may test lubricants in different ways, making the results incomparable. DIN 51354 standards ensure that results are consistent across tests and laboratories.
• Quality control: Helps lubricant manufacturers assess and maintain the quality and performance of their products. Ensures products meet minimum performance criteria.
• Product development: Engineers and chemists use data to develop better lubricants with higher wear resistance.
• Industry specification: Many industries (automotive, aerospace, manufacturing) specify harmonized data in the DIN 51354 standard when selecting lubricants for machinery.
• Safety and reliability: Ensuring low wear under load increases machine life and safety, which is critical in high-load or high-speed applications.

DIN 51354 standards are generally used for automotive gear and engine oils, industrial lubricants for bearings and gears, and hydraulic and turbine oils. For companies involved in lubricant testing or machine design, compliance with this standard helps ensure products are durable, efficient, and accepted by the industry.

Our organization, which has been supporting businesses across all sectors for years through a wide range of testing, measurement, analysis, and evaluation activities, has a strong team of employees who closely follow global developments in science and technology and are constantly improving themselves. In this context, we also provide testing services in accordance with the DIN 51354 "Testing of lubricants - Determination of the shear stability of polymer-containing lubricating oils."