Gas oil gas is a group of petroleum distillation products having boiling points between kerosene and lubricating oil. The term originally referred to the product of oil gas works that was added to the product of coal gas works to produce improved illuminating gas.
Historically (c.1924) 40% of traditionally distilled crude oil would be Gas oil—”being too heavy to burn in wick fed lamps and not heavy enough to make lubricating oils”
Vacuum gas oil is a more viscous form of oil gas, produced by vacuum distillation. It is black semi-solid with a smell like asphalt.
for Gas Oil analysis see the link below: