Fuel oil: This covers all residual (heavy) fuel oils (including those obtained by blending). Kinematic viscosity is above 10 cSt at 80°C. The flash point is always above 50°C and density is always more than 0.90 kg/l. -Low sulphur content: heavy fuel oil with sulphur content lower than 1%. - High sulphur content: heavy fuel oil with sulphur content of 1% or higher.