Ethanol Fuel Mixtures

By SRT-Tom · Nov 5, 2021 · ·
  1. SRT-Tom
    The question frequently comes up, “Are E10 and E85 fuels harmful to my engine?” Here is everything you wanted to know about the chemical compound ethanol that is added to gasoline.

    Ethanol is used as an “oxygenate” and is added to fuel to help reduce hydrocarbon emissions that cause air pollution. It is highly refined beverage (grain) alcohol, approximately 200-proof, that can be produced from natural products such as corn, sugar cane and wheat. New technology allows ethanol to be made from cellulose-rich feedstocks including corn stalks, grain straw, paper, pulp, wood chips, municipal waste, switchgrass and other sources.


    Ethanol fuel mixtures have "E" numbers which describe the percentage of ethanol fuel in the mixture by volume. They are designated E5, E10, E15, E20, E25, E70, E75, E85, E95 and E100. The most common is E10. The use of ethanol blends in conventional gasoline vehicles is restricted to low mixtures, as ethanol is corrosive and can degrade some of the materials in the engine and fuel system. Also, the engine has to be adjusted for a higher compression ratio as compared to a pure gasoline engine to take advantage of ethanol's higher oxygen content, thus allowing an improvement in fuel efficiency and a reduction of tailpipe emissions.


    Your car’s owner manual will state which blended fuels are safe to use (Note- typically up to E10).



    The term “ethanol-blended fuel,” or E10, refers to fuel that contains 10% anhydrous ethanol and 90% gasoline. Not all states require gas pumps to be labeled to indicate the presence of ethanol in the fuel, so you may be currently using E10 fuel and not be aware of it. There have been efforts in Washington D.C. to introduce gas with 15% ethanol (E15).


    E10, sometimes called gasonol, can be used in all cars made from 2011 without the need for any modification of the engine or fuel system. It has been tested and deemed a safe and reliable fuel. However, repeated use of E10 in incompatible vehicles could damage it over time. Classic car owners and those that drive older vehicles must continue filling up with E5. The use of higher blends in older engines can result in lowered fuel mileage, metal corrosion, deterioration of plastic and rubber fuel system components, clogged fuel systems, fuel injectors, and carburetors, delamination of composite fuel tanks, varnish buildup on engine parts, damaged or destroyed internal engine components, water absorption, fuel phase separation, and shortened fuel storage life.


    E10 blends are typically rated as being 2 to 3 octane numbers higher than regular gasoline and are approved for use in all new U.S. automobiles. The E10 blend and lower ethanol content mixtures have been used in several countries, and its use has been primarily driven by the several world energy shortages that have taken place since the 1973 oil crisis.
    It also reduces carbon monoxide (CO) emissions by 20 to 30% under the right conditions.


    Other common low percentage blends are E5 and E7. These concentrations are generally safe for recent engines that should run on pure gasoline. In 2006, mandates for blending bioethanol into vehicle fuels were enacted in 36 states/provinces and 17 countries at the national level, with most mandates requiring a blend of 10 to 15% ethanol with gasoline.


    E15 contains 15% ethanol and 85% gasoline. This is generally the highest ratio of ethanol to gasoline that is possible to use in vehicles recommended by some auto manufacturers to run on E10 in the US. This is due to ethanol's hydrophilia and solvent power.

    As a result of the Energy Independence Security Act of 2007, which mandates an increase in renewable fuels for the transport sector, the U.S. Dept. of Energy began assessments for the feasibility of using intermediate ethanol blends in the existing vehicle fleet as a way to allow higher consumption of ethanol fuel. The National Renewable Energy Laboratory (NREL) conducted tests to evaluate the potential impacts of intermediate ethanol blends on legacy vehicles and other engines. In a preliminary report released in October 2008, the NREL presented the results of the first evaluations of the effects of E10, E15 and E20 gasoline blends on tailpipe and evaporative emissions, catalyst and engine durability, vehicle driveability, engine operability, and vehicle and engine materials. This preliminary report found none of the vehicles displayed a malfunction indicator light as a result of the ethanol blend used; no fuel filter plugging symptoms were observed; no cold start problems were observed at 75°F and 50°F laboratory conditions; and as expected, computer technology available in newer model vehicles adapts to the higher octane causing lower emissions with greater horsepower and in some cases greater fuel economy.

    In October 2010, the EPA granted a waiver to allow up to 15% of ethanol blended with gasoline to be sold only for cars and light pickup trucks with a model year of 2007 or later, representing about 15% of vehicles on U.S. roads. In January 2011, the waiver was expanded to authorize use of E15 to include model year 2001 through 2006 passenger vehicles.

    The National Association of Convenience Stores, which represents most gasoline retailers, considers the potential for actual E15 demand is small, "because the auto industry is not embracing the fuel and is not adjusting their warranties or recommendations for the fuel type." A solution to the infrastructure barriers was the introduction of blender pumps that allowed consumers to turn a dial to select the desired level of ethanol.


    In June 2011 EPA, in cooperation with the Federal Trade Commission issued its final ruling regarding the E15 warning label required to be displayed in all E15 fuel dispensers in the U.S. to inform consumers about what vehicles can, and what vehicles and equipment cannot, use the E15 blend.


    In order to adjust to EPA regulations, U.S. automobile manufacturers started to make their vehicles E15 compatible (GM in 2012, Ford in 2013 and FCA in 2016). GM warned, however, that for model year 2011 or earlier vehicles, they strongly recommended that its customers refer to their owners manuals for the proper fuel designation for their vehicles.

    E20, E25

    E20 contains 20% ethanol and 80% gasoline, while E25 contains 25% ethanol. These blends have been widely used in Brazil since the late 1970s. As a response to the 1973 oil crisis, the Brazilian government made mandatory the blend of ethanol fuel with gasoline, fluctuating between 10% to 22% from 1976 until 1992. Due to this mandatory minimum gasoline blend, pure gasoline (E0) is no longer sold in Brazil. A federal law was passed in October 1993 establishing a mandatory blend of 22% anhydrous ethanol (E22) in the entire country. This law also authorized the Executive to set different percentages of ethanol within pre-established boundaries, and since 2003, these limits were fixed at a maximum of 25% (E25) and a minimum of 20% (E20) by volume. Since then, the government has set the percentage on the ethanol blend according to the results of the sugar cane harvest and ethanol production from sugarcane, resulting in blend variations even within the same year. All Brazilian automakers have adapted their gasoline engines to run smoothly with this range of mixtures, thus, all gasoline vehicles are built to run with blends from E20 to E25.

    E70, E75

    E70 contains 70% ethanol and 30% gasoline, while E75 contains 75% ethanol. These blends, known as winter E85, are used in the U.S. and Sweden for E85 flexible-fuel vehicles to avoid cold starting problems at low temperatures (i.e., below 32 degrees F).


    E85 is intended only for engines specially designed to accept high-ethanol content fuel blends, such as the Flexible Fuel Vehicles (FFV) made by some car companies. It is generally the highest ethanol fuel mixture found in the U.S. and several European countries, particularly in Sweden, as this blend is the standard fuel forflexible-fuel vehicles. This mixture has a high octane rating of 108 and it is a form of "chemical supercharging."



    E100 is pure ethanol fuel. Straight hydrous ethanol as an automotive fuel has been widely used in Brazil since the late 1970s for neat ethanol vehicles and more recently for flexible-fuel vehicles. The ethanol fuel used in Brazil is distilled close to the azeotrope mixture of 95.63% ethanol and 4.37% water (by weight) which is approximately 3.5% water by volume.

    The higher fuel efficiency of E100 (compared to methanol) in high performance race cars resulted in Indianapolis 500 races in 2007 and 2008 being run on 100% fuel-grade ethanol.

    Share This Article


To view comments, simply sign up and become a member!