Low Sulphur - Marine Fuels explained

Marine Fuels explained

Managing the Transition to 2020 Low-Sulphur Regulations

Marine Fuels explained

All marine fuel oils start as crude oil, varying in composition depending on its source. Crudes differ in proportion of hydrocarbons (paraffins, napthenes, asphaltenes), density and sulphur content (sweet vs. sour crude). Crude oil is processed first by distillation (atmospheric, and later vacuum), then by catalytic cracking, to increase the yield of high-demand and high-margin lighter products such as gasoline, jet fuel and diesel. What’s left is residual oil, the largest component of marine fuel oils. Oil grades are mixed by refiners to obtain specific properties complying with ISO standards; ship engines are designed to run with specific grades.

3.5% Intermediate Fuel Oil

  • A heavy fuel used in all large marine engines; blends residual oil with lighter distillates
  • Contains up to 3.5% sulphur
  • IFO 380: most common and has 98% residual oil and a viscosity of 380 centistokes (cSt)
  • IFO 180: lighter blend with 88% residual oil and a viscosity of 180 cSt
  • Requires heating and purification on board

2.0% Marine Diesel Oil (MDO)

  • A distillate containing trace amounts of residual fuel oil
  • Maximum sulphur content of 2%
  • Lower viscosity (10-30 cSt)
  • Can be used in smaller engines without requiring heating

0.1% Marine Gas Oil (MGO)

  • A pure distillate
  • Sulphur limits vary; the standard for use near shore in Europe and the US in SECAs is 0.1%, while the cap for car and truck diesel in most countries is 70-100 times lower
  • Even lower viscosity than MDO (6 cSt)
  • Similar to home heating oil and diesel used by cars and trucks
  • Has increasingly displaced MDO with the expansion of SECAs

0% Biodiesel

  • From plant sources
  • Sulphur-free
  • A component in car and truck fuel (the EU allows up to 7% biodiesel in diesel)
  • Little use or testing by engine manufacturers for merchant shipping, though some navies are currently testing them