ISO 13357-2:2017

Overview

ISO 13357-2:2017 - "Petroleum products - Determination of the filterability of lubricating oils - Part 2: Procedure for dry oils" - specifies a laboratory method to evaluate the filterability of dry, mineral-based lubricating oils (notably hydraulic oils). The method measures how readily an oil will pass fine filters used in hydraulic systems, using a membrane filtration test and two defined assessment stages (Stage I and Stage II). Results are reported as dimensionless filterability percentages averaged over three determinations.

Key topics and technical requirements

• Scope and limitations

  • Applies to mineral-based oils, evaluated up to ISO viscosity grade (VG) 100 (ISO 3448).
  • Not suitable for some oils containing insoluble additives, very large molecular species, or fluids incompatible with the test membrane (e.g., many fire‑resistant fluids).
  • Oils containing water or used at high temperature require ISO 13357-1 assessment.

• Test principle

  • Oil is filtered through a mixed cellulose ester membrane (47 mm diameter, mean pore size 0.8 µm) under controlled pressure.
  • Filtration rates and times for defined filtrate volumes are recorded; filterability is calculated from ratios of early vs later filtration rates/volumes.

• Defined measurements

  • Stage I filterability: compares initial flow behaviour to a reference volume (procedure uses a 240 ml-based comparison).
  • Stage II filterability: compares the initial flow rate to the flow rate between 200 ml and 300 ml of filtered volume - more sensitive to gels and fine silts.

• Apparatus and conditions

  • Stainless-steel filtration apparatus with an effective filtration area (approx. 1 130 mm² ± 60 mm²).
  • Compressed dry gas supply with regulated pressures (nominally 50–200 kPa).
  • Measuring cylinder (250 ml, additional graduations up to 300 ml) and timing device; oven for heating to 70 °C ± 10 °C when required.
  • Use of reagent-grade wash solvents, filtered isopropyl alcohol and clean water per referenced ISO methods.

• Result reporting

  • Average of three determinations; test report includes conditions, membranes batch/source, and any deviations.

Applications and who uses it

• Quality control and R&D laboratories testing hydraulic oils and lubricants for fine-filter systems.
• Oil manufacturers benchmarking product filterability for hydraulic applications.
• Maintenance engineers, equipment OEMs and procurement teams specifying oils for systems with fine filtration (e.g., mobile and industrial hydraulics).
• Regulatory and certification bodies needing standardized test evidence of filtration performance.

Related standards

• ISO 13357-1 - Effect of water and high temperature on filterability
• ISO 3448 - Viscosity classification (VG grades)
• ISO 3170 - Sampling of petroleum liquids
• ISO 3696, ISO 4788, ISO 1219-1 - referenced laboratory and equipment requirements

Keywords: ISO 13357-2:2017, filterability test, lubricating oils, hydraulic oils, membrane filtration, 0.8 µm membrane, Stage I, Stage II, ISO viscosity grade.