High Octane Fuels: Challenges & Opportunities

This fact sheet from the Environmental and Energy Study Institute (EESI) examines the potential for deploying mid-level ethanol blends (E25 to E40) as high-octane fuels in the United States. It discusses the technical benefits for engine efficiency, the existing compatibility of the vehicle fleet and retail infrastructure, and the potential for significant greenhouse gas (GHG) reductions compared to conventional gasoline.

• Mid-level ethanol blends between 25 and 40 percent (E25 to E40) can improve fuel efficiencies and lower overall greenhouse gas (GHG) emissions for the existing passenger vehicle fleet compared to the standard 10 percent blend (E10).
• A significant portion of the current U.S. vehicle fleet is compatible with higher ethanol blends: over 80 percent of cars on the road (model year 2001 and newer) are certified for E15, and there are 17.4 million FlexFuel Vehicles (FFVs) capable of using blends up to 85 percent ethanol.
• Higher octane fuels, such as those provided by ethanol, allow for higher compression ratios, turbocharging, and downsizing/downspeeding, which increase engine efficiency and mile-per-gallon ratings.
• While some infrastructure upgrades are needed for mid-level blends, the costs for equipment to support blends between E15 and E25 are moderate; however, the cost for equipment capable of handling E26 to E85 is considered a serious barrier to market penetration.
• The potential for GHG reductions varies by ethanol source and blend: corn ethanol can reduce lifecycle GHGs by 19 to 48 percent relative to gasoline, while a nationwide E25 blend with a 5 percent fuel economy gain could reduce transportation sector GHG intensity by 5 to 9 percent. A mid-level E40 blend from cellulosic ethanol could achieve up to 30 percent GHG reductions.
• The Department of Energy's Co-Optimization of Fuels and Engines (Optima) Initiative aims to reduce per-vehicle petroleum consumption by 30 percent by 2030, which could save consumers up to $50 billion and reduce petroleum consumption by 4.5 billion barrels.

APA

Environmental and Energy Study Institute (2015). High Octane Fuels: Challenges & Opportunities. https://www.eesi.org/files/FactSheet_High_Octane_Fuels_061115.pdf

Chicago

Environmental and Energy Study Institute. High Octane Fuels: Challenges & Opportunities. 2015. https://www.eesi.org/files/FactSheet_High_Octane_Fuels_061115.pdf.

Wikipedia

{{cite report |author=Environmental and Energy Study Institute |title=High Octane Fuels: Challenges & Opportunities |date=June 2015 |url=https://www.eesi.org/files/FactSheet_High_Octane_Fuels_061115.pdf |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{environmentalandenergystudyinstitute2015high, author = {{Environmental and Energy Study Institute}}, title = {{High Octane Fuels: Challenges \& Opportunities}}, institution = {Environmental and Energy Study Institute}, year = {2015}, month = jun, url = {https://www.eesi.org/files/FactSheet_High_Octane_Fuels_061115.pdf}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }