08 Jun Fuel Quality Management for Vessels in Extended Idle
London, (Oilandgaspress) Since the closure of the Strait of Hormuz to most commercial shipping in late February 2026, an estimated 1,550 vessels, carrying approximately 20,000 seafarers, have been unable to transit, or have chosen to remain at anchor in the Arabian Gulf, Gulf of Oman, and approaches. Traffic through the Strait, which normally averages around 138 vessels per day, has fallen to near-zero on most days. The conflict began on 28 February 2026, resulting in vessels being idle for approximately 90 days. Many are expected to remain idle until a navigable resolution to the situation emerges, which cannot be predicted at this time.
For vessel owners and operators responsible for such vessels, there is a need to focus on the technical consequences of extended idle upon fuel quality and what needs to be done in order to protect the vessel, crew and the environment.
Fuel Quality Deterioration During Extended Idle
Fuel deterioration in idle vessels is caused by a combination of time, temperature, water ingress, and inactivity. Each mechanism reinforces the others. The Arabian Gulf summer (June–September) is one of the most demanding storage environments in global shipping, with bunker tank temperatures on unshaded anchored vessels regularly reaching 50–55°C.
Biofuel Blends
The UAE, principally Fujairah and Jebel Ali, has begun supplying ISCC-certified marine biofuel blends, primarily FAME (UCOME) blended into VLSFO, at concentrations typically ranging from B10 to B30 (10–30% FAME by volume). Vessels that bunkered Biofuel blends before going idle face additional degradation risks that do not apply to conventional fuel:
FAME can cause filter blockage. Depending on feedstock composition, may be susceptible to crystallisation at lower temperatures. Therefore, Wax Appearance Temperature testing should be performed before re-activation for any vessel sailing to cooler latitudes post-Gulf.
FAME (UCOME) blends, may exhibit reduced storage stability. Although storage life varies, a typical shelf life is often considered to be around 3 to 4 months, after which the risk of oxidation, acid formation and microbial contamination may increase, particularly under elevated ambient temperatures.
FAME is hygroscopic and absorbs water from tank atmospheres, promoting microbial growth at rates significantly higher than conventional VLSFO. Here, the free-water monitoring frequency should be doubled for any tank containing a biofuel blend.
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