ISO 8217 Marine Fuel Specifications — Practical Guide

What ISO 8217 covers

ISO 8217 is the international standard defining the minimum quality requirements for marine residual and distillate fuels. It specifies grade categories (RMA, RMB, RMD, RME, RMG, RMK for residual; DMA, DMB, DMZ, DFA etc. for distillate), quality parameters for each grade, and test methods. The current edition is ISO 8217:2024, though 2017 remains widely referenced.

Key residual grades explained

RMG 380 is the historical workhorse — maximum viscosity 380 cSt at 50°C. RMG 180 is lighter. RMK grades are higher density and viscosity. Post-IMO 2020, any of these can be specified at 0.50% or 3.50% maximum sulphur. VLSFO is typically RMG-range low-sulphur; HSFO is RMG-range high-sulphur.

Distillate grades explained

DMA is the standard marine gas oil — light distillate, no residual component, ≤1.50% sulphur in base spec. DMZ is similar. DMB is a distillate with limited residual content. For ECA compliance, 0.10% sulphur (LSMGO) specification is required and should be explicitly stated.

Critical quality parameters

Viscosity at 50°C (residual) or 40°C (distillate) — determines pumping, heating, and atomisation. Density at 15°C — affects injection and quantity conversion. Flash point — minimum 60°C (safety). Pour point — affects cold-flow behaviour. Water content — higher values indicate contamination. Sediment — mechanical/chemical filterable content. Cat fines (aluminium + silicon) — critical for two-stroke engine wear; 60 ppm max per ISO 8217 but many operators specify 40 ppm. CCAI (calculated carbon aromaticity index) — ignition quality indicator.

ISO 8217:2024 changes

The 2024 edition introduced provisions for biofuel blends (FAME content limits), improved guidance on stability and compatibility testing, and addressed emerging fuel types. The 2017 edition remains referenced in many commercial contracts during the transition.

Reading a bunker quality certificate

Key things to check: grade designation matches your order (e.g., RMG 380 VLSFO 0.50%), all parameters within spec, test lab accreditation (ISO 17025 is standard), and date of testing. Dispute any parameter out of spec or anomalous values. Third-party laboratory testing of retained samples is common for material disputes.