A clean-burning fuel with an upgraded mixture of hydrocarbons is produced by reacting methane-containing gas with crude oil or a liquid petroleum fraction in a process wherein the gas is fed to a reaction vessel to contact both the liquid and a metallic catalyst grid that is formed from windings of a transition metal supported on an iron frame immersed in a liquid petroleum fraction, at a moderate temperature to produce a gaseous reaction product which is condensed to form the fuel. The fuel has a variety of uses, including serving as an additive to crude oil for transport purposes.
