VPS has reported an increase in shale oil components in marine fuels bunkered in Singapore, specifically VLSFO, raising concerns despite no operational issues reported from vessels using these fuels. Testing in February and March 2026 revealed that 90,000 metric tons of VLSFO contained compounds linked to Estonian Shale Oil, known for potentially destabilizing fuel and causing sludge formation.
Estonian Shale Oil includes high-boiling phenolic compounds, leading to elevated acid numbers, sometimes exceeding the ISO 8217 limit of 2.5 KOH/g. Recent samples in Singapore showed concentrations of resorcinol and alkyl benzenediols between 4,000-13,200 ppm with acid numbers ranging from 1.98 to 2.34 KOH/g. While these fuels may initially comply with ISO 8217, the presence of such compounds can pose long-term operational risks, including filter blockages and impacts on fuel injection systems.
VPS recommends precautionary measures for handling these fuels, including enhanced monitoring of fuel treatment systems, avoiding unnecessary fuel co-mingling, and maintaining detailed records of fuel transfers and consumption. Additionally, vessels should seek clarification from suppliers regarding blend components and any elevated acid numbers associated with shale oil.
