Petroleum gas is a group of refined products having a boiling point between kerosene and lubricating oil. The term originally referred to the product of oil and gas works, which was added to the product of coal gas factories to produce an improved illuminating gas.

Historically (c.1924) 40% of traditionally distilled crude oil would be gas oil - “too heavy to burn in wick lamps, and not hard enough to lubricate oils”