A Brief History of Octane in Gasoline: From Lead to Ethanol

The document traces the evolution of octane boosters in the United States, from the early use of tetraethyl lead to the current reliance on the BTEX complex and ethanol. It details how health concerns—such as lead poisoning in children and groundwater contamination from MTBE—led to regulatory phase-outs under the Clean Air Act and its amendments. The author argues that increasing ethanol blends (specifically mid-level blends between E25 and E40) can enhance engine efficiency, lower greenhouse gas emissions, and reduce the health risks associated with petroleum-based aromatics.

• Tetraethyl lead was the primary octane provider in the U.S. until the mid-1970s, but its use caused severe health issues, particularly in children, including anemia, behavioral disorders, low IQ, and nerve damage. The EPA estimates that 68 million children were exposed to toxic levels of lead from leaded gasoline between 1927 and 1987.
• Methyl tertiary butyl ether (MTBE) was used in 87 percent of reformulated gasoline (RFG) by the late 1990s to reduce ozone precursors. However, it was phased out by 2005 after the EPA and U.S. Geological Survey found it contaminated groundwater supplies in 20 percent of RFG areas.
• The BTEX complex (benzene, toluene, ethyl-benzene, and xylene) increased in use as a substitute for lead, reaching roughly one-third of the gasoline pool by 1990 and up to 50 percent in premium grades. These aromatics are linked to carcinogenic and mutagenic effects, as well as cardio-pulmonary and neurodegenerative disorders through the formation of ultra-fine particulates (UFP) and polycyclic aromatic hydrocarbons (PAHs).
• Ethanol is presented as a cleaner, low-toxicity alternative to petroleum-based octane boosters. Increasing ethanol content from 10 to 15 percent is anticipated to reduce cancer risk from tailpipe emissions by 6.6 percent. While some evidence suggests older cars may emit more nitrous oxide (NOX) with ethanol, studies on 2012 model year vehicles showed no increase in NOX emissions between E10, E15, and E20 blends.
• The document advocates for a national transition to mid-level ethanol blends between E25 and E40. Such a transition would enable the use of smaller, more efficient engines with higher compression ratios, thereby reducing petroleum consumption and lifecycle greenhouse gas emissions.

APA

Environmental and Energy Study Institute (2016). A Brief History of Octane in Gasoline: From Lead to Ethanol. https://www.eesi.org/files/FactSheet_Octane_History_2016.pdf

Chicago

Environmental and Energy Study Institute. A Brief History of Octane in Gasoline: From Lead to Ethanol. 2016. https://www.eesi.org/files/FactSheet_Octane_History_2016.pdf.

Wikipedia

{{cite report |author=Environmental and Energy Study Institute |title=A Brief History of Octane in Gasoline: From Lead to Ethanol |date=March 2016 |url=https://www.eesi.org/files/FactSheet_Octane_History_2016.pdf |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{environmentalandenergystudyinstitute2016brief, author = {{Environmental and Energy Study Institute}}, title = {{A Brief History of Octane in Gasoline: From Lead to Ethanol}}, institution = {Environmental and Energy Study Institute}, year = {2016}, month = mar, url = {https://www.eesi.org/files/FactSheet_Octane_History_2016.pdf}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }