A Brief History of Octane

The document traces the evolution of octane sources in the U.S., from the use of tetraethyl lead to petroleum-based aromatics (BTEX) and ethanol. It details the health risks associated with lead and BTEX, the regulatory phase-outs mandated by the EPA under the Clean Air Act, and the potential for mid-level ethanol blends (E25 to E40) to enable more fuel-efficient engines and lower greenhouse gas emissions.

• Tetraethyl lead was the preferred octane provider starting in 1921 due to low costs, but it caused severe health issues, including anemia, behavioral disorders, and nerve damage in children. The EPA began phasing it out in the mid-1970s, eventually banning it for on-road vehicles in 1996.
• Following the lead phase-out, the refining industry increased the use of the BTEX complex (benzene, toluene, ethyl-benzene, and xylene). BTEX volume rose from 22% to approximately one-third of the gasoline pool by 1990, reaching up to 50% in premium grades.
• Exposure to the BTEX complex and its combustion products, such as ultra-fine particulates (UFP) and polycyclic aromatic hydrocarbons (PAHs), is linked to carcinogenic and mutagenic effects, as well as cardio-pulmonary and neurodegenerative disorders.
• Methyl tertiary butyl ether (MTBE) was used in 87% of reformulated gasoline (RFG) by the late 1990s to reduce ozone precursors, but it was phased out by 2005 after the EPA found it threatened groundwater supplies.
• Ethanol is a low-toxicity octane provider with a pure rating over 100. Increasing ethanol content from 10% to 15% is anticipated to reduce cancer risk from tailpipe emissions by 6.6%.
• Transitioning to mid-level ethanol blends between E25 and E40 could enable the design of highly fuel-efficient engines, reducing petroleum consumption and lifecycle greenhouse gas emissions.

APA

Stolark, J. (2016). A Brief History of Octane. Environmental and Energy Study Institute. https://www.eesi.org/papers/view/fact-sheet-a-brief-history-of-octane

Chicago

Stolark, Jessie. A Brief History of Octane. Environmental and Energy Study Institute, 2016. https://www.eesi.org/papers/view/fact-sheet-a-brief-history-of-octane.

Wikipedia

{{cite report |last1=Stolark |first1=Jessie |title=A Brief History of Octane |publisher=Environmental and Energy Study Institute |date=30 March 2016 |url=https://www.eesi.org/papers/view/fact-sheet-a-brief-history-of-octane |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{stolark2016brief, author = {Stolark, Jessie}, title = {{A Brief History of Octane}}, institution = {Environmental and Energy Study Institute}, year = {2016}, month = mar, url = {https://www.eesi.org/papers/view/fact-sheet-a-brief-history-of-octane}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }