A fuel quality advisory issued by testing firm Maritec-Naias has raised concerns about the quality of some very low sulphur fuel oil (VLSFO) delivered in Singapore, with elevated catfine levels and acid numbers detected across multiple samples.
What the Testing Revealed
According to Ship & Bunker, Maritec-Naias analysed five VLSFO samples collected from two bunker suppliers between May 20 and June 2, 2026. The results showed aluminium and silicon (Al+Si) concentrations — commonly referred to as catfines — ranging from 61 mg/kg to 68 mg/kg.
While the ISO 8217 specification sets a limit of 60 mg/kg for catfines, Ship & Bunker notes the reported values remain within accepted testing tolerance. That said, the findings sit at the upper boundary of what is considered acceptable.
Why Catfines Matter
Catfines are highly abrasive particles that, if not adequately removed by onboard fuel treatment systems, can cause significant mechanical damage. The wear risk extends to fuel system components, piston rings, and cylinder liners — components that are costly and time-consuming to repair or replace.
Acid Numbers Also a Concern
Separately, the same advisory flagged findings from 15 additional VLSFO samples, which returned acid numbers between 2.0 mg KOH/g and 2.5 mg KOH/g. As reported by Ship & Bunker, while these values remain within specification, Maritec-Naias noted they are elevated and may be associated with contaminants linked to sludge formation, fuel pump seizures, and injector fouling.
The testing firm recommended enhanced monitoring and additional testing for any fuels showing elevated acid numbers.
Recommendations from Maritec-Naias
In response to these findings, Maritec-Naias advised buyers operating in Singapore to:
- Request a Certificate of Quality prior to bunkering
- Conduct additional monitoring and testing of fuels with elevated acid numbers
- Ensure onboard fuel treatment systems are functioning effectively to manage catfine contamination
Does This Matter to You?
This advisory is directly relevant to anyone purchasing VLSFO in Singapore. The findings span samples from two separate suppliers, suggesting the issue is not isolated to a single source. Elevated catfines near or at specification boundaries leave little margin for error, particularly if onboard purification systems are not operating at full efficiency. Combined with elevated acid numbers that approach the upper end of acceptable ranges, these results point to fuel quality conditions that warrant closer attention during the bunkering process and onboard fuel management.
Shipping stakeholders calling at Singapore or planning stems in the near term would be prudent to factor these findings into their fuel procurement and testing strategies.
Gulf Bunkering does not provide operational or security guidance. This article is for informational purposes only. Operators should consult flag state authorities, P&I clubs, and relevant advisories for decisions relating to transit planning.
Sources: Ship & Bunker
