combustible in liquid form extracted from petroleum oils by fractional distillation. It is divided into the following, in order of increasing viscosity: domestic fuel oil; light fuel oil; heavy fuel oil no.1; heavy fuel oil no.2, oils obtained as residues in the distillation of petroleum; used, either alone or mixed with other oils, for domestic heating and for furnace firing (particularly marine furnaces); also as fuel for internal combustion engines, kütusena kasutatav õli