Refers to petroleum-based liquid fuels used for heating, power generation, or marine engines. Often used in technical, industrial, or regulatory contexts.
This factory uses fuel oil to run its boilers.
Fuel oil for ships is also called heavy oil.
軽油 is diesel fuel or light oil, which is a lighter fraction than heavy fuel oil. 燃料油 can include both light and heavy oils.
ガソリン is gasoline/petrol, a light fuel for spark-ignition engines. 燃料油 typically refers to heavier liquid fuels and does not usually include gasoline.
Compound of 燃料 (nenryō, 'fuel') and 油 (yu, 'oil').