At the turn of the century, the process of refining black gold was still fairly simple. Distillation produced kerosene, a cheap illuminant, and naphtha, a byproduct used as a lubricant and solvent. With the growth of the automotive industry and the spread of the internal-combustion engine in the late 19th century, though, gasoline refining became far more important. New methods of production evolved, from William M. Burton's thermal-cracking technique in 1913 to Frenchman Eugene Houdry's catalytic-cracking process, developed in the late 1930s. Houdry's method underlies modern petroleum refining. Lead was added in the 1920s to reduce engine knock but began to be eliminated for health reasons in the 1980s.

Related Links
"History of Petroleum"