ISO 26422:2014

Overview - ISO 26422:2014 (Shear stability of lubricating oils)

ISO 26422:2014 specifies a laboratory method to determine the shear stability of polymer-containing lubricating oils using a tapered roller bearing mounted in a four-ball machine. The method measures permanent viscosity loss after subjecting the fluid to high shear and allows prediction of in-service viscosity degradation for high-shear applications. It is especially suitable for lubricants used in gears, roller bearings and other components exposed to severe shear conditions.

Key topics and technical requirements

• Test principle: Splash lubrication of 40.0 ml ± 0.5 ml of oil in a tapered roller bearing operated at controlled speed and load; kinematic viscosity is measured at 100 °C before and after shearing.
• Viscosity loss metric: Percentage viscosity loss = (viscosity_before − viscosity_after) / viscosity_before × 100. A small value indicates high resistance to shear-induced viscosity loss.
• Standard test parameters (typical):
  • Temperature: 60 °C ± 1 °C (test), pre-heat and control required
  • Load: 5 000 N ± 200 N
  • Speed: 1 475 min−1 ± 25 min−1
  • Quantity: 40.0 ml ± 0.5 ml
  • Duration: 1 740 000 ± 500 motor revolutions (≈ 20 h); alternative durations may be used for different applications but precision is established for the specified duration.
• Equipment and materials: Four-ball machine as per ISO 20623, tapered roller bearing (recommended SKF 32008 X/Q), viscometer per ISO 3104/3105, temperature control and validated test apparatus. Use of alternate bearings or apparatus requires validation.
• Validation & reporting: Procedures for running-in and validating test bearings, referencing with control fluids, and reporting percentage viscosity loss are specified. Precision statements and referencing harmonized with CEC L‑45‑99.

Applications - who uses ISO 26422:2014

• Lubricant formulators assessing polymer shear stability for additive selection and product development.
• OEMs and component designers (transmissions, axles, bearings) requiring realistic high-shear performance data.
• Independent test laboratories and QC teams performing acceptance and batch verification of polymer-containing oils.
• R&D teams comparing test methods-ISO 26422 subjects fluids to a higher shear rate than injector-nozzle tests (e.g., ISO 20844) and is preferred for severe, gear/roller-bearing conditions.

Related standards

• ISO 20623 - four-ball machine requirements (used to drive the test)
• ISO 3104 / ISO 3105 - kinematic viscosity measurement methods and instrumentation
• ISO 20844 - diesel injector nozzle shear test (lower shear-rate alternative)
• CEC L‑45‑99 and DIN 51350‑6 - equivalent/related methods referenced in the development of ISO 26422

Keywords: ISO 26422:2014, shear stability, lubricating oils, tapered roller bearing, viscosity loss, polymer-containing oils, four-ball machine, KRL test method.