Kettering's research in fuel was based on his belief that oil would be in short supply and additives would allow more efficient engines with higher compression. His "high percentage" solution was to mix ethanol with gasoline, while his "low percentage solution" looked for additives that would be added in small quantities to increase what later would be called the octane rating of gasoline. Thomas Midgley Jr. and Kettering identified tetraethyllead (TEL) in December 1921 as an additive that would eliminate engine knocking at a dilution of one thousand to one. While use of ethanol could not be patented, TEL's use as an additive could. Kettering and Midgley secured its patent and proceeded to promote the use of TEL as an additive instead of other options. Kettering became the first president of the newly founded Ethyl Corporation that started to produce TEL in 1923. One year later, he hired Robert A. Kehoe as the medical expert to proclaim that leaded gasoline was safe for humans. That its use was an ecological disaster leading to a global lead contamination was not acknowledged until many decades later.