Ship operators face growing risks from bunker fuels that pass standard ISO 8217 testing but later cause serious operational problems, according to Lloyd's Register’s Fuel Oil Bunker Analysis and Advisory Service (FOBAS) in its latest fuel quality report.
The Scope of the Problem
While off-specification fuels remain a persistent challenge, the most disruptive cases in the first half of 2026 involved fuels that met routine compliance requirements but exhibited poor stability or compatibility or contained non-conventional blend components uncovered only through forensic analysis, as reported by Lloyd's Register.
In March and April 2026, multiple vessels reported operational difficulties after taking fuel at a major bunkering hub. Detailed investigation by FOBAS found that many of these fuels contained elevated concentrations of Estonian shale oil, in some cases estimated at 10–15%. Although shale oil is recognized as an acceptable blend component under ISO 8217, FOBAS determined that higher concentrations can be associated with fuel instability and problems affecting filters, separators, and fuel pumps.
Persistent Off-Spec Issues
Off-spec cases remained elevated throughout the six-month period, indicating that quality issues have become a persistent feature of the marine fuel supply chain rather than isolated events, according to the report. The most common recurring problems include:
- Sulphur exceedances
- Excessive water
- Sediment and stability issues
- Elevated catalytic fines
- Sodium contamination
- Low flash point distillates
| Issue | Description |
|---|---|
| Sulphur exceedances | Fuel sulphur content above regulatory limits |
| Excessive water | Water content beyond acceptable thresholds |
| Sediment and stability | Particulate matter and chemical instability |
| Elevated catalytic fines | Abrasive particles from refining catalysts |
| Sodium contamination | Sodium compounds affecting combustion |
| Low flash point distillates | Volatile components posing safety risks |
Biofuels and Blending Complexity
Biofuels continue to grow in the marine fuel mix without emerging as a primary source of trouble, according to Lloyd's Register. Where issues occurred in blended fuels, they were generally traced to the conventional VLSFO (very low sulphur fuel oil) component rather than the FAME (fatty acid methyl ester) fraction.
Operational Implications for Ship Operators
“The challenge is no longer simply identifying fuels that fail specification. Increasingly, operators are encountering fuels that meet the required limits but still create operational difficulties once they are stored, handled and used onboard,” said Murray Kirkwood, fuel specialist consultant at Lloyd's Register. He added: “As fuel blending becomes more complex, the distinction that matters is increasingly not between on-spec and off-spec fuel, but between fuels that are operationally resilient and fuels that are operationally fragile.”
With marine fuels becoming ever more diverse, Lloyd's Register argues that effective fuel management now hinges on understanding fuel behavior rather than relying solely on pass-or-fail testing.
Recommended Actions for Ship Operators
- Implement forensic fuel analysis beyond routine ISO 8217 testing to detect non-conventional blend components like shale oil.
- Monitor fuel stability and compatibility through laboratory testing and onboard observation.
- Maintain detailed records of fuel sources and blend compositions to trace operational issues.
- Work with bunker suppliers to ensure transparency about blend components, especially in complex blended fuels.
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