E85 is an abbreviation for an ethanol fuel blend of 85% denatured ethanol fuel and 15% gasoline or other hydrocarbon by volume, although the exact ratio of fuel ethanol to hydrocarbon can vary considerably while still carrying the E85 label. The ethanol content is adjusted according to the local climate to maximize engine performance. ASTM 5798 specifies the allowable fuel ethanol content in E85 as ranging from 51% to 83%. E85 is commonly used by flexible-fuel vehicles (FFV) in the United States and Europe. In the United States, government subsidies of ethanol in general and E85 in particular have encouraged a growing infrastructure for the retail sale of E85, especially in corn growing states in the Midwest.
One purported advantage of E85 over conventional gasoline is a reduction in exhaust emissions, if one disregards the fact that E85 increases the emissions of acetaldehyde from vehicles. Additionally, there is a greater potential for localized production of ethanol in agricultural areas and utilization of waste materials. Also, a diversification of fuel sources reduces dependence on any one particular type of fuel and may increase stability of supply.
E85 promoters contend that automotive manufacturers currently fail to equal the fuel economy of gasoline because they fail to take advantages of characteristics which are superior in ethanol-based fuel blends. They claim that some ethanol engines have already produced 22% more miles per gallon than identical gasoline engines.
Excessive fuel pulse width modulation
Ethanol promoters[who?] claim that today's FFV are much too inexact in measuring the ethanol content because car companies will not pay the high patent royalties demanded for fuel content sensors. They[who?] state that some FFV have used wastefully high-flow fuel injectors which are not necessary and waste fuel all the time on either fuel. The technical term is "excessive fuel pulse width modulation".
Other ethanol advocates[who?] also state that it is a mistake to base ethanol engine design on gasoline engine design, but that ethanol engines should be based on diesel engine design parameters instead.[clarification needed] Using this approach, the EPA has produced an ethanol-only engine which achieves much higher brake thermal efficiency levels than gasoline engines achieve.
In contrast, ethanol critics contest the benefits of E85 by focusing on the fact that E85 has 33% less energy content than 100% gasoline (and 30% less than the E10 gasohol blend that is sold by almost all retailers in the US). The amount of reduction in mileage, therefore, is highly dependent upon the particulars of the vehicle design, exact composition of the ethanol-gasoline blend, and state of engine tune (primarily fuel-air mixture and compression ratio). In order to offset this change in fuel economy there has been much legislation passed to subsidize the cost. The American Jobs Creation Act of 2004 created the Volumetric Ethanol Excise Tax Credit (VEETC) to subsidize the production costs. In 2008, the 2008 Farm Bill changed the 51-cent tax credit provided by VEETC to 45 cents. There have been other measures taken by congress to jump start ethanol production. For instance, the 2004 VEETC bill provided for a Small Ethanol Producer Tax Credit which gave tax credits to small ethanol producers. More recently the Tax Relief, Unemployment Insurance Reauthorization, and Job Creation Act of 2010 extended the tax cuts allowed by VEETC that were set to expire at the end of 2010 until the end of 2012.
So in order to save money at the pump with current FFV available in the United States, the price of E85 must be much lower than gasoline. E85 was at least 20% less expensive in most areas, as recently as 2011. However, as of March 2012, the difference in the retail price between E85 and gasoline is 15% or less in the vast majority of the United States.  E85 also gets less MPG, at least in FFV. In one test, a Chevy Tahoe FFV averaged 18 MPG [U.S. gallons] for gasoline and 13 MPG for E85, or 28% fewer MPG than gasoline. In that test, the cost of gas averaged $3.42, while the cost for E85 averaged $3.09, or 90% of the cost of gasoline. In another test, however, a fleet of Ford Tauruses averaged only about 6% fewer miles per gallon in the ethanol-based vehicles as compared to traditional, gas-powered Tauruses.
Octane and performance
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Use in flexible-fuel vehicles
E85 ethanol is used in engines modified to accept higher concentrations of ethanol. Such FFV are designed to run on any mixture of gasoline or ethanol with up to 85% ethanol by volume. There are a few major differences between FFVs and non-FFVs. One is the elimination of bare magnesium, aluminum, and rubber parts in the fuel system. Another is that fuel pumps must be capable of operating with electrically conductive ethanol instead of non-conducting dielectric gasoline fuel. Fuel injection control systems have a wider range of pulse widths to inject approximately 34% more fuel. Stainless steel fuel lines, sometimes lined with plastic, and stainless-steel fuel tanks in place of terne fuel tanks are used. In some cases, FFVs use acid-neutralizing engine oil. For vehicles with fuel-tank-mounted fuel pumps, additional differences to prevent arcing, as well as flame arrestors positioned in the tank's fill pipe, are also sometimes used.
As more effort is put into maximizing an engine to take advantage of E85's higher "octane", engines achieve greater power advantages. One car that has higher power on ethanol is the Koenigsegg CCXR, which on ethanol is the third-most powerful production car, with 20% more hp on E85 than on gasoline. According to the manufacturer, this is due to the cooling properties of ethanol. E85 has an octane rating higher than that of regular gasoline's typical rating of 87, or premium gasoline's 91-93. This allows it to be used in higher-compression engines, which tend to produce more power per unit of displacement than their gasoline counterparts. The Renewable Fuels Foundation states in its Changes in Gasoline IV manual, "There is no requirement to post octane on an E85 dispenser. If a retailer chooses to post octane, they should be aware that the often cited 105 octane is incorrect. This number was derived by using ethanol’s blending octane value in gasoline. This is not the proper way to calculate the octane of E85. E85's true ethanol content should be used to calculate E85’s octane value. This results in an octane range of 94-96 (R+M)/2. These calculations have been confirmed by actual-octane engine tests." 
Examples of this mis-citation can be found at the Iowa Renewable Fuels Association titled "E85 Facts" which cites a range of 100-105, and a document at the Texas State Energy Conservation Office titled "Ethanol", which cites a 113 rating.
Some vehicles can actually be converted to use E85 despite not being specifically built for it. Because of the lower heating value E85 has a cooler intake charge—which, coupled with its high stability level from its high octane rating—has also been used as a "power adder" in turbocharged performance vehicles. These modifications have not only resulted in lower GHG emissions, but also resulted in 10-12% power and torque increase at the wheels. Because of its low price (less than $2.00/gal in some places) and high availability in certain areas people have started to turn to using it in place of high-end racing fuels, which typically cost over $10.00/gal.
E85 consumes more fuel in FFV when the vehicle uses the same compression ratio for both E85 and gasoline, because of its lower air–fuel ratio and lower heating value.
Use of gasoline in an engine with a high enough compression ratio to use E85 efficiently would likely result in catastrophic failure due to premature fuel ignition, as the octane rating of gasoline is not high enough to withstand the greater compression ratios in use in an engine specifically designed to run on E85. Using E85 in a gasoline engine has the drawback of achieving lower fuel economy, as more fuel is needed per unit air (stoichiometric ratio) to run the engine in comparison with gasoline. The additional ethanol required for a stoichiometric fuel ratio helps compensate for lack of energy provided by ethanol's lower heating value (LHV), which is lower than the LHV of gasoline.
When environmentalists concern themselves with emissions from combustion engines, there are four primary types of pollutants scientists study. These emissions are hydrocarbons (HC), oxides of nitrogen (NOx), carbon monoxide (CO) and carbon dioxide (CO2). Because E85 is predominantly ethanol, the exhaust emissions are much different from those of regular gasoline. Numerous studies have compared and contrasted the different emissions and the effects these emissions have on the environment, but the tests have been inconclusive. The tests have shown very little consistency if any at all because there are too many variables involved. The make and model of the vehicle, the way in which the ethanol was produced and the vehicle's overall fuel efficiency all play a large role in the overall outcome of each study. To address the problem of inaccuracy, engineers at the National Renewable Energy Laboratory combined data from all applicable emissions studies and compiled them into one data set. This compiled set of data showed that on average all emissions that are federally regulated showed a decrease or no statistically relevant difference between E85 and gasoline.
EPA's stringent tier-II vehicle emission standards require that FFVs achieve the same low emissions level regardless whether E85 or gasoline is used. However, E85 can further reduce emissions of certain pollutants as compared to conventional gasoline or lower-volume ethanol blends. For example, E85 is less volatile than gasoline or low-volume ethanol blends, which results in fewer evaporative emissions. Using E85 also reduces carbon-monoxide emissions and provides significant reductions in emissions of many harmful toxics, including benzene, a known human carcinogen. However, E85 also increases emissions of acetaldehyde. EPA is conducting additional analysis to expand our understanding of the emissions impacts of E85.
Food vs. fuel
E85 critics contend that production of ethanol from corn drives up world food prices, causing corn to be unaffordable or even unavailable. E85 advocates counter that allegation by pointing out that over 93% of all corn grown in the United States is never fed to people, but is instead used as livestock feed. As livestock cannot digest starch efficiently, and dried corn is mostly starch, it is simply transformed into fecal matter and not into products directly useful to humans. American farmers grow more corn than people purchase; there is an annual surplus of corn in the U.S.
E85 advocates say that corn prices have increased due to manipulation of the commodities markets and because American corn companies sell more and more US-grown corn to Mexico and China, creating more competition for corn buyers, and therefore driving up its price. E85 critics contend that ethanol producers may not reduce carbon emissions due to the petroleum and natural gas used in raising corn and refining it. E85 advocates reply by pointing to ethanol producers who do not do so, but instead use E85 or biodiesel fuel to transport E85, and use biomass as a heat source for the distillation of ethanol instead of petro-products like natural gas.
Some say that cellulosic ethanol produced from waste materials or fast growing non-food crops such as switchgrass is much more beneficial, but not yet economically practical at large scale. Others say that the world can easily replace all of its use of petroleum by simply making ethanol from the many crops that yield more ethanol per acre than corn yields, with existing technology, not future technology, and that certain elements in the cellulosic ethanol field are more interested in patent rights than in producing the greatest amount of ethanol at the lowest price point.
Availability and price
E85 is increasingly common in the United States, mainly in the Midwest where corn is a major crop and is the primary source material for ethanol-fuel production. As of July 1, 2014, there were more than 3,300 fuel stations that offered E85 fuel. E85 as a fuel is widely used in Sweden; however, most of it is imported from Italy and Brazil. E85 was formerly available from the Maxol chain in Ireland, where it was made from whey, a byproduct of cheese manufacturing. The availability ended in 2011, due to a severe excise-duty hike which rendered it economically unviable. In Finland E85 is available from 26 St1 chain locations. The E85 sold by St1 is labeled as RE85 to indicate it is manufactured from bio-waste.
- Alcohol fuel
- Earth's atmosphere
- Lambda sensor – also known as an oxygen sensor, used to measure lean versus rich combustion conditions
- Methanol – wood alcohol, not to be confused with ethanol (grain alcohol)
- Timeline of alcohol fuel
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- Flex-Fuel Bait and Switch - See how many flex-fuel cars are on the road and how many stations offer E85. Center for American Progress
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- Flex-fuel Bait and Switch - See how many flex-fuel cars are on the road and how many fuel stations offer E85.
- US biofuel production should be suspended, UN says