Common ethanol fuel mixtures

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, and mandated in some areas for emissions and other reasons.

In 2002, the U.S. used as motor fuel, ethanol equal to 137,000 terajoules (3.8×1010 kWh), the energy equivalent of 1.13 billion US gallons (4.3 gigalitres) of gasoline.

When the measurements are normalized, the difference becomes 1.0%, a result that is highly consistent with an estimation of calorific values based on approximate fuel composition, which came out at 1.1% in favour of E5.

[65] The National Renewable Energy Laboratory (NREL) conducted tests to evaluate the potential impacts of intermediate ethanol blends on legacy vehicles and other engines.

[65][66] 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 24 °C (75 °F) and 10 °C (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.

[68] 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.

Retailers have shunned building infrastructure due to the costly regulatory requirements which have created a practical barrier to the commercialization of the higher blend.

Both the Alliance of Automobile Manufacturers and the National Petrochemical and Refiners Association complained that relying solely on this warning label is not enough to protect consumers from misfueling.

Among other arguments, the groups argued that the higher ethanol blend is not only a problem for cars, but also for fuel pumps and underground tanks not designed for the E15 mixture.

The case was thrown out on a technical reason, as the court ruled the groups did not have legal standing to challenge EPA's decision to issue the waiver for E15.

[85] In November 2013, the Environmental Protection Agency opened for public comment its proposal to reduce the amount of ethanol required in the U.S. gasoline supply as mandated by the Energy Independence and Security Act of 2007.

This limit, known as the "blend wall," refers to the practical difficulty in incorporating increasing amounts of ethanol into the transportation fuel supply at volumes exceeding those achieved by the sale of nearly all gasoline as E10.

Based on the Japanese/German results, a minimum of 2 vol.% or 2.52% m/m water is currently proposed in the revision of the hydrous ethanol specification for blending in petrol at E10+ levels.

[91] The level of blending above 10% (V/V) is chosen both from a technical (safety) perspective and to distinguish the product in Europe from regular unleaded petrol for reasons of taxes and customer clarity.

Small-scale tests have shown many vehicles with modern engine types can run smoothly on this hydrous ethanol blend.

As avoiding mixing with E0, in particular at extremely low temperatures, in logistic systems and engines is not recommended, a separate specification for controlled usage is presented in a Netherlands Technical Agreement NTA 8115.

[96] As a response to the 1973 oil crisis, the Brazilian government made mandatory the blend of ethanol fuel with gasoline, fluctuating between 10% and 22% from 1976 until 1992.

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.

[105][106] Thailand introduced E20 in 2008,[107] but shortages in ethanol supplies by mid-2008 caused a delay in the expansion of the E20 fueling station network in the country.

[109] The rapid growth in E20 demand is because most vehicle models launched since 2009 were E20-compatible, and sales of E20 are expected to grow faster once more local automakers start producing small, E20-compatible, fuel-efficient cars.

A study commissioned by BP and published in September 2013, concluded that the use of advanced biofuels in the UK, and particularly E20 cellulosic ethanol, is a more cost-effective way of reducing emissions than using plug-in electric vehicles (PEVs) in the timeframe to 2030.

[114] The seasonal reduction of the ethanol content to an E85 winter blend is mandated to avoid cold starting problems at low temperatures.

This mixture has an octane rating of 108, however, the Ethanol molecule also carries with it an oxygen atom, where-as gasoline does not, effectively requiring the internal combustion engine to ingest less air per unit-volume by its own accord, which reduces pumping losses, and further increases the exo-thermic chemical reaction.

[2] In Brazil, the first Scania ED95 bus with a modified diesel engine was introduced as a trial in São Paulo city in December 2007, and since November 2009, two ED95 buses were in regular service.

[139] In November 2010, the municipal government of São Paulo city signed an agreement with UNICA, Cosan, Scania and Viação Metropolitana, a local bus operator, to introduced a fleet of 50 ethanol-powered ED95 buses by May 2011.

[139] The 50 ED95 buses had a cost of R$ 20 million (US$12.3 million) and due to the higher cost of the ED95 fuel and the lower energy content of ethanol as compared to diesel, one of the firms participating in the cooperation agreement, Raísen (a joint venture between Royal Dutch Shell and Cosan), supplies the fuel to the municipality at 70% of the market price of regular diesel.

[154] E100 imposes a limitation on normal vehicle operation, as ethanol's lower evaporative pressure (as compared to gasoline) causes problems when cold starting the engine at temperatures below 15 °C (59 °F).

[160][161] Swedish carmakers have developed ethanol-only capable engines for the new Saab Aero X BioPower 100 Concept E100, with a V6 engine which is fuelled entirely by E100 bioethanol,[162][163] and the limited edition of the Koenigsegg CCXR, a version of the CCX converted to use E85 or E100, as well as standard 98-octane gasoline, and currently the fastest and most powerful flex-fuel vehicle with its twin-supercharged V8 producing 1018 hp when running on biofuel, as compared to 806 hp on 91-octane unleaded gasoline.

[166] The use of ethanol blends in conventional gasoline vehicles is restricted to low mixtures, as ethanol-gasoline is corrosive and can degrade some of the materials in the engine and fuel system.

This information is based on the modifications made by the Brazilian automotive industry at the beginning of the ethanol program in that country in the late 1970s, and reflects the experience of Volkswagen do Brasil.