HOF Car
A turbocharged gasoline direct injection vehicle is being modified to implement technologies such as high compression pistons to take advantage of the higher octane fuel.

High Octane Fuel Study

In vehicles designed for its use, high octane fuel blends have the potential to increase vehicle efficiency through improved knock suppression. When the high-octane blend is made with 25-40% ethanol by volume, efficiency improvements of 5-10% are sufficient to offset the reduced vehicle range often associated with the decreased volumetric energy density of the fuel (such as with flexible-fuel vehicles (FFVs) fueled with E85). The prospects for a high-octane, mid-level ethanol blend are attractive because it could be used legally in the 18 million FFVs currently on the road. Thus the current FFV fleet could provide an immediate market for the new fuel so that it is widely available as high-efficiency vehicles designed to use it are entering the market.

Project Details

The Bioenergy Technologies Office of DOE EERE has sponsored a “scoping study” to assess the potential of high-octane fuel (HOF) to assess its potential to reduce energy consumption and greenhouse gas (GHG) emissions, and to understand barriers to its successful market introduction. The goal was to provide information about the benefits of bringing this new fuel to the market, barriers to its adoption, and strategies for market introduction.

The current project, which began in late FY 2013 and culminates in early FY 2016, uses the combined expertise of Argonne National Laboratory, the National Renewable Energy Laboratory, and the Oak Ridge National Laboratory. It builds upon ongoing work at these national labs funded by DOE.

Task Descriptions

The HOF project consists of the following integrated tasks:

Efficiency Gains of HOF in Dedicated Vehicles: Quantify the fuel economy benefits of HOF at the vehicle level. Significant efficiency improvements are possible through a combination of improved engine thermal efficiency and improved system efficiency from downspeeding and downsizing.

Description of Properties for Engine Knock Resistance: Develop a description of fuel knocking resistance that considers octane numbers and heat of vaporization; include the development of methods of measuring the heat of vaporization of ethanol–gasoline blends.

Effects of HOF on Legacy FFVs: Determine the effects of high-octane gasoline blends, such as blends of gasoline with 25-40% ethanol (E25-E40) on legacy FFVs. Demonstrating a performance benefit in legacy FFVs would help in marketing ethanol blends for the legacy FFV fleet, which could bolster development of the infrastructure for fueling future vehicles specifically designed for this fuel.

Analysis of Energy and GHG Emissions and Modeling of Refinery Impacts: Conduct petroleum refinery simulations for various ethanol blending levels and HOF market shares. Evaluate the “well-to-wheels” energy and GHG effects of HOF use, accounting for vehicle efficiency gains, refinery operation changes, and the blending effects of ethanol.

Market Analysis: Identify and assess the economic, logistical, behavioral, and regulatory barriers to introducing HOF to the market and ways to address these barriers during a transition period. Stakeholders were engaged to help identify barriers and ways to overcome them and to estimate their potential impact on dedicated HOF vehicle sales and ethanol use.

Infrastructure Assessment: Work with stakeholders to assess the compatibility of mid-level ethanol blends with the existing storage and fueling infrastructure.

Evaluation of Cost Reduction Potential of HOF Blendstocks: Evaluate the potential to use natural gasoline as a low-cost blendstock for HOF.

Pertinent Findings and Outcomes

  • E25 and E40 would achieve volumetric fuel economy parity with today’s E10 with a 5 and 10% improvement in vehicle efficiency, respectively (i.e., fuel economy would be the same using HOF as today’s vehicle using E10, and so every gallon of ethanol used in HOF would displace a full gallon of gasoline.)
  • Fuel efficiency gains of up to 10% over E10 were demonstrated in vehicles with turbocharged, direct-injected engines. Operating engines in more efficient but more knock-prone conditions—through downspeeding, downsizing, and increasing the compression ratio—improves efficiency with HOF. The exact fuel economy benefit will vary depending on ultimate engine/vehicle design and driving conditions.
  • Measurements of heat of vaporization of ethanol blended with a range of gasoline blendstocks, including natural gasoline; show that there is little difference between the hydrocarbon components and that the major factors affecting ethanol blend heat of vaporization are ethanol content and temperature. Research is ongoing under other DOE programs to understand how octane number and heat of vaporization interact for fuel knock resistance.
  • Most legacy FFVs offer a performance benefit (i.e., improved acceleration) using HOF with no engine modifications required. This finding is a potential marketing pathway for introducing high octane mid-level blends, because they are legal to use in today’s FFV fleet. For “normal driving,” fuel economy using HOF was proportional to the energy density of the fuel.
  • The efficiency gain of HOF overwhelmingly overtakes the potential increase in refinery GHG emissions for HOF production, resulting in net GHG reductions by HOF.
  • Modeling further suggests that even under very aggressive market penetration assumptions, the availability of ethanol feedstocks does not limit the growth of the market. Fuel retailers’ willingness to invest in HOF equipment does limit market penetration in many scenarios. In scenarios where the latter is not a limiting factor, the construction rate of biorefineries (and technology advancement for second-generation ethanol) tends to be a limiting factor in early years, and HOF vehicle adoption tends to be the limiting factor in later years.
  • Modeling further suggests that even under very aggressive market penetration assumptions, the availability of ethanol feedstocks does not limit the growth of the market. Fuel retailers’ willingness to invest in HOF equipment does limit market penetration in many scenarios. In scenarios where the latter is not a limiting factor, the construction rate of biorefineries (and technology advancement for second-generation ethanol) tends to be a limiting factor in early years, and HOF vehicle adoption tends to be the limiting factor in later years.
  • The use of E25–E40 for producing HOF allows for greater market penetration of HOF than is available through E10 HOF.
  • Producing HOF with E10, E25 or E40 in petroleum refineries causes minimal impact on overall refinery efficiency. However, if HOF market penetration is significant, petroleum refineries will find it hard to meet the high demand for HOFs without the use of higher-ethanol blends (e.g., E25 and E40).
  • Based on our model analysis, optimized HOF vehicles can achieve a substantial market share (43 to 79% of vehicle stock by 2035) and can consume significant quantities of ethanol (up to 30 billion gallons per year). The extent of market success for the vehicles and fuel varies widely depending on the scenario and underlying assumptions.
  • Although the retail fueling station infrastructure is not inherently compatible with mid-level ethanol blends today, materials and equipment are available that are compatible with 25–40% ethanol blends. The cost of dispensing equipment is substantially less for E25.
  • Nearly all fuel terminals store ethanol and while there are no technical issues for storing more ethanol there are considerations including tank availability—nearly all are in use and a considerable amount are leased through long term contract to terminal customers. There could be space constraints for additional tanks and ethanol unloading facilities and the regulatory process for these additions are lengthy.
  • An empirical model was developed to estimate fuel properties using natural gasoline as a blendstock.
  • Natural gasoline is a potential low-cost hydrocarbon blendstock for FFV fuels and HOF, if blended with sufficient ethanol.

GHG reductions for two sets of vehicle efficiency improvement assumptions are shown.

Assuming 5% improvement in gasoline-equivalent fuel economy (mpgge) results in advanced E25 vehicles having volumetric fuel economy parity with today’s vehicles with E10.

HOF Chart
Well to wheel Greenhouse Gas analysis shows the reductions with GHG using HOF as a function of efficiency improvements, ethanol content and source

High Octane Fuel Content in KDF

Title Abstract Published
Summary of High-Octane, Mid-Level Ethanol Blends Study

The DOE Bioenergy Technologies Office initiated a collaborative research program between Oak Ridge National Laboratory (ORNL), the National Renewable Energy Laboratory (NREL), and Argonne National Laboratory (ANL) to investigate HOF in late 2013. The program objective was to provide a...

2016
High Octane Fuel: Terminal Backgrounder

The Bioenergy Technologies Office of the U.S. Department of Energy Office of Energy
Efficiency and Renewable Energy sponsored a scoping study to assess the potential of ethanolbased
high octane fuel (HOF) to reduce energy consumption and greenhouse gas emissions.
HOF blends...

2016
Properties of Ethanol Fuel Blends Made with Natural Gasoline

This project looks at the potential of blending ethanol with natural gasoline to produce Flex-Fuels (ASTM D5798-13a) and high-octane, mid-level ethanol blends. Eight natural gasoline samples were collected from pipeline companies or ethanol producers around the United States.

2014
Heat of Vaporization Measurements for Ethanol Blends Up to 50 Volume Percent in Several Hydrocarbon Blendstocks and Implications for Knock in SI Engines

The objective of this work was to measure knock resistance metrics for ethanol-hydrocarbon blends with a primary focus on development of methods to  measure the heat of vaporization (HOV). Blends of ethanol at 10 to 50 volume percent were prepared with three gasoline blendstocks and a natural...

2014
Well-to-Wheels Greenhouse Gas Emissions Analysis of High-Octane Fuels with Various Market Shares and Ethanol Blending Levels

High-octane fuels (HOFs) such as mid-level ethanol blends can be leveraged to design vehicles with increased engine efficiency, but producing these fuels at refineries may be subject to energy efficiency penalties.  It has been questioned whether, on a well-to-wheels (WTW) basis, the use of HOFs...

2014
High-Octane Mid-Level Ethanol Blend Market Assessment

The United States government has been promoting increased use of biofuels, including ethanol from non-food feedstocks, through policies contained in the Energy Independence and Security Act of 2007. The objective is to enhance energy security, reduce greenhouse gas (GHG) emissions, and provide...

2015
Increasing Biofuel Deployment and Utilization through Development of Renewable Super Premium: Infrastructure Assessment

This report evaluates infrastructure implications for a high-octane fuel, i.e., a blend of 25% denatured ethanol and 75% gasoline (E25) or higher (E25+), for use with a new high-efficiency type of vehicle. E25+ is under consideration due to federal regulations requiring the use of more renewable...

2014
High Octane Fuels: Challenges & Opportunities

Fact Sheet for High Octane Fuels: Challenges & Opportunities

2015
Effects of High-Octane Ethanol Blends on Four Legacy Flex-Fuel Vehicles, and a Turbocharged GDI Vehicle

The U.S. Department of Energy (DOE) is supporting engine and vehicle research to investigate the potential of high-octane fuels to improve fuel economy. Ethanol has very high research octane number (RON) and heat of vaporization (HoV), properties that make it an excellent spark ignition engine...

2015
Regulatory and Commercial Barriers to Introduction of Renewable Super Premium

Presentation at Biomass 2013 July 31 - August 1, 2013

2013
Increasing Biofuel Deployment through Renewable Super Premium

Presentation at 2015 Bioenergy Technologies Office Peer Review March 23, 2015

2015
Overview of High Octane Fuel Engine and Vehicle Efforts

Presentation at Auto/Ag/Ethanol Meeting USCAR August 18, 2015

2015
Benefits of High Octane, Mid-Level Ethanol Fuel Blends

Share and discuss provisional findings from coordinated DOE national laboratory studies on the opportunities and challenges associated with the deployment of high octane, mid-level ethanol blend transportation fuels.

2015
High Octane Ethanol Blends for Improved Vehicle Efficiency

Presentation to Hudson Institute Fueling American Growth Washington, DC May 7, 2015

2015
Higher Ethanol Blends for Improved Efficiency

Presentation at National Ethanol Conference Grapevine, TX February 20, 2015

2015
Making Better Use of Ethanol as a Transportation Fuel With “Renewable Super Premium”

Presentation at Biomass 2013 Meeting

2013
Compatibility Assessment of Elastomer Materials to Test fuels Representing Gasoline Blends Containing Ethanol and Isobutanol

The compatibility of elastomeric materials used in fuel storage and dispensing applications was determined for test fuels
representing neat gasoline and gasoline blends containing 10 and 17 vol.% ethanol, and 16 and 24 vol.% isobutanol. The
actual test fuel chemistries were based...

2013
Compatibility Assessment of Plastic Infrastructure Materials with Off-Highway Diesel and a Diesel Blend Containing 20 Percent Fast Pyrolysis Bio-Oil

The compatibility of plastic materials used in fuel storage and dispensing applications was determined for an off-highway diesel fuel
and a blend containing 20% bio-oil (Bio20) derived from a fast pyrolysis process. Bio20 is not to be confused with B20, which is a
diesel blend...

2014
Compatibility Assessment of Plastic Infrastructure Materials with Test fuels Representing E10 and iBu16

The compatibility of plastic materials used in fuel storage and dispensing applications was determined for a test fuel representing
gasoline blended with 10% ethanol. Prior investigations were performed on gasoline fuels containing 25, 50 and 85% ethanol, but the
knowledge gap...

2014
Compatibility Assessment of Plastic Infrastructure Materials to Test Fuels Representing Gasoline Blends Containing Ethanol and Isobutanol

The compatibility of plastic materials used in fuel storage and dispensing applications was determined for test fuels representing gasoline blended with 25 vol.% ethanol and gasoline blended with 16 and 24 vol.% isobutanol. Plastic materials included those used in flexible plastic piping and...

2013