Viscosity of Heavy Fuel Oil - Residual Fuel Oil
Fuel oil is a fraction obtained from petroleum distillation, either as a distillate or a residue. Fuel oil is classified in six classes, numbered 1 through 6, according to its boiling point, composition and purpose.
- No. 1: Similar to kerosene. It is the fraction that boils off right after gasoline.
- No. 2: This is the diesel fuel that trucks and cars run on, leading to the name "road diesel".
- No. 3: This is a distillate fuel oil and is rarely used.
- No. 4: This fuel oil is usually a blend of distillate and residual fuel oils, such as No. 2 and No. 6; sometimes it is just a heavy distillate (~ diesel distillate or residual fuel oil).
- No. 5: It is a mixture of 75% to 80% of No. 6 and 25% to 20% of No. 2.
- No. 6: This oil is called residual fuel oil (RFO) or heavy fuel oil (HFO). It is the remainder of the crude oil after gasoline and distillate fuel oils have been extracted through distillation. It fuels thermal power stations or robust engines.
In fuel oil, the viscosity is highly significant since it indicates both the relative ease with which the oil can be pumped, and the ease of atomization. Density alone is of little significance as an indication of the burning characteristics of fuel oil. Used in conjunction with other properties, it is of value in mass-volume relationships and for the specific energy of an oil.
Viscosity Tables – Measurement data
HFO and RFO (ASTM D396)
Viscosity classification according to ASTM D396.
|Fuel Oil||Kin. Viscosity [mm²/s] at 40°C||Kin. Viscosity [mm²/s] at 100°C||API Gravity °API|
|No. 1||1.3 ... 2.1||−||38 ... 45|
|No. 2||1.9 ... 3.4||−||30 ... 38|
|No. 4 light||1.9 ... 5.5||−||24 ... 28|
|No. 4||5.5 ... 24||−||20 ... 24|
|No. 5 light||−||5.0 ... 8.9||17 ... 22|
|No. 5||−||9.0 ... 14.9||14 ... 18|
|No. 6||−||15 ... 50||8 ... 15|
Fuel Oil No. 6 (SVM™)
Examples for viscosity readings of different No. 6 fuel oils obtained by SVM™. This oil type is usually also measured at 50 °C.
|No. 6 Fuel Oils||Kin. Viscosity [mm²/s] at 50°C||Kin. Viscosity [mm²/s] at 100°C|
Measurement with SVM™
|Reference||ASTM D396, measurement with SVM™|
|Related||Heavy oil, heavy fuel, residual fuel oil, HFO, RFO, heating oil, viscosity, ASTM D396|