ISO 3987:2024

Overview

ISO 3987:2024 - "Petroleum products - Determination of sulfated ash in lubricating oils and additives and fatty acid methyl esters" - defines a laboratory test method for measuring the mass fraction of sulfated ash in unused lubricating oils (with additives), additive concentrates and fatty acid methyl esters (FAME). The procedure covers samples with sulfated ash from 0.005 % to 25.00 % and was updated to include FAME and revised precision statements. It is not intended for used engine oils containing lead or for non-additive lubricating oils (see Related Standards).

Key topics and technical requirements

• Scope & applicability: Unused lubricating oils containing metallic additives (barium, calcium, magnesium, zinc, potassium, sodium, tin) and FAME; restricted use below 0.02 % for non-metal-containing (ashless) additive products.
• Analytical principle: Carbonize and ignite the test portion, treat the residue with concentrated sulfuric acid, then heat in a muffle furnace at 775 °C until constant mass; repeat acid treatment and ignition as required.
• Reagents & apparatus:
  • Sulfuric acid (≥98 %), sulfuric acid (1+1), propan-2-ol, toluene, low-ash mineral oil for dilution.
  • Evaporating dish/crucible (porcelain, fused silica or platinum as appropriate), electric muffle furnace (775 °C ± 25 °C), balance capable of 0.1 mg.
• Sampling & sample size: Laboratory samples taken per ISO 3170 / ISO 3171; test portion selection guidance (do not exceed 80 g); dilute high-ash additives if needed.
• Quality & reporting:
  • Sulfuric acid blank required for very low ash tests.
  • Reporting precision: results to 0.001 % for ≤0.02 % ash, and to 0.01 % for higher levels.
  • Precision data (repeatability and reproducibility) are provided in the standard.

Practical applications

• Quality control for lubricant and additive manufacturers - monitor formulation metal content and ash contribution from additives.
• Biodiesel and FAME testing - verify sulfated ash in FAME feedstocks and blends.
• Independent test laboratories - standard method for contractual testing and certification.
• OEMs and regulatory compliance - ensure lubricants meet engine and emissions system requirements related to ash-forming elements.
• R&D and formulation - evaluate impact of additives (e.g., zinc dialkyldithiophosphates) on final ash levels.

Related standards

• ISO 6245 - recommended method for non-additive lubricating oils (where ISO 3987 is not applicable).
• ISO 3170 / ISO 3171 - sampling of petroleum liquids (referenced for sample collection).
• ISO 3696 - laboratory water quality for reagents.

Safety note: the method uses hazardous reagents (concentrated sulfuric acid, toluene, high-temperature furnaces). Appropriate laboratory safety procedures are required.

Keywords: ISO 3987:2024, sulfated ash determination, lubricating oils, FAME, test method, sulfuric acid, muffle furnace, lubricant additives, quality control.