Sunday, February 28, 2016
Tetra Ethyl Lead and the AMOCO alternative
From my The Automobile and American Life, chapter 3:
Success came to Charles Franklin Kettering and Thomas Midgley related to tetra-ethyl lead during the early 1920s. Around 1920 there was a fear that the world was running out of oil, and therefore leading automobile industry executives thought that engines had to be designed to run more efficiently. One way to do this was to increase the compression ratio of the engine, or the volume swept in the cylinder by the piston, but increased compression ratios led to pre-detonation of the fuel-air mixture, a phenomenon that was called knocking. Kettering initiated a search for an additive to prevent knocking, and after many trials, discovered an organo-metallic substance called tetra-ethyl lead, or TEL. There was one hitch with this project, however. Lead compounds had been known since Roman times, to be notoriously poisonous, but it was claimed that in the ratio of 1:1300 in gasoline, the material was harmless. TEL was seen by industry leaders as a “gift from God;” tests made by laboratories after 1925 demonstrated that TEL was supposedly safe for mechanics, gas station attendants and consumers.12 Of course, as we know now, it was not. At low levels lead proved to be a neuro-toxin, but it would remain until the 1960s before improved chemical instrumentation demonstrated the extent of the public health dangers posed by this substance. Beginning in the 1970s, TEL was phased out in the U.S., but only after two generations were exposed to relatively high amounts of lead that eventually entered the human body.
There is much one can add to the TEL story. However, only recently was I reminded that there is another angle to this story, namely the sale of lead-free AMOCO (American Oil Company) gasoline between the 20s and the 70s, long before lead-free gasoline was the norm. During the late 1960s and early 1970s there was plenty of controversy over catalytic converter technology and the poisoning of the catalyst by lead compounds added to the gasoline. Industry critics continually argued that catalytic converters were impractical and that government mandates for air pollution abetment were unreasonable. Amoco premium lead free gasoline was sold only in the east and south between 1915 and 1970. In a May 1970 Motor Trend article, writer John Ethridge asserted that "there's an overwhelming mass of evidence that unleaded gasoline will ruin most engines...." The issue centered on valve problems on one hand, and more hydrocarbon emissions that are subject to photochemical reactions.
Yet, scientific evidence from studies at Ford and DuPont pointed to lead deposits in an engine increased exhaust emissions. Studies followed during the early 1970s validating the feasibility of lead free gasoline coupled with platinum-activated converters. . Furthermore, there was unequivocal evidence that TEL actually wore out spark plugs and exhaust systems prematurely!
Dr. Ted B. Tom, vice president of R&D at Amoco correctly foresaw the future when in 1971 he predicted that "when lead free gasoline is combined with catalytic converter systems, the auto will disappear from the black list of polluters." (MT, 2/1971, p. 12).