The ability for gasoline to withstand being compressed is most important for vehicles that run on traditional gasoline. In contrast, diesel engines do not compress fuel but rather air and then inject fuel. These engines rely on different ratings, known as cetane numbers. The main difference between whether or not one uses high or low octane gasoline is determined by the level of "knocking" ones engine experiences. Inside the engine, an air-fuel mixture is ignited by the spark plug.
While this is occurring, the piston is also moving upwards, compressing the air-fuel mixture and simultaneously increasing its temperature since temperature increases as pressure increases. With lower octane fuels, the air-fuel mixture can also ignite due to this compression. When this flame front collides with the flame front ignited by the spark plug, an audible "knock" is heard. Learn more. The right fuel for your vehicle Get the most out of your engine, and your journey, with Exxon and Mobil SynergyTM gasoline and diesel.
Get more out of every trip Explore our comprehensive list of tips to help you improve fuel efficiency and get more out of every trip. All trademarks used herein are trademarks or registered trademarks of Exxon Mobil Corporation or one of its subsidiaries. In mandating cleaner fuels, through reformulated gasoline and other programs, EPA has reduced the volume of aromatics to between 25 to 28 percent of the conventional gasoline pool, though some health professionals question the safety of even these levels.
After the lead phase-out, there were early concerns regarding the BTEX complex. Today, health research indeed suggests that even very low-level exposure to the BTEX complex, from gasoline additives and other petroleum products, may contribute to negative developmental, reproductive and immunological responses, as well as cardio-pulmonary effects. Upon incomplete combustion of the BTEX complex contained in gasoline, ultra-fine particulates UFP and polycyclic aromatic hydrocarbons PAHs are formed, which carry their own adverse health impacts even at low levels.
Both UFP and PAHs have also been linked to developmental and neurodegenerative disorders, cancers, and cardio-pulmonary effects. Considerable attention has been given to benzene in fuel, as it is highly toxic. At the same time, the partial replacement of benzene with other aromatic compounds xylene, ethyl-benzene, toluene may not be sufficient in reducing exposure to BTEX's toxic effects. The other aromatics, such as toluene and xylene, are not capped.
Early automakers expressed interest in plant-based alcohol fuels, such as ethanol. Henry Ford designed the first Model T to run on ethanol. But, at the time, gasoline was a much cheaper fuel. During the oil embargo, regular unleaded gasoline prices jumped 57 percent and routine gasoline shortages also occurred. These events, and the regulation of many air pollutants, sparked a renewed interest in fuel efficiency, electric vehicles, and renewable fuels such as ethanol, which were seen as ways to meet the new regulations and reduce petroleum consumption.
Today, the majority of ethanol in the United States is blended with gasoline to produce E10 10 percent ethanol, 90 percent gasoline. Over 95 percent of gasoline sold in the United States is E In addition to having lower lifecycle greenhouse gas emissions than conventional gasoline, ethanol is an excellent octane provider, with neat pure ethanol having an octane rating of over Ethanol, which is generally the cheapest octane provider, is then used to bring the octane rating of the gasoline up to the labelled octane value on the gas pump.
For example, 84 octane gasoline is typically blended with 10 percent ethanol to reach the minimum octane requirement of 87 for retail gasoline. Currently, there are two ways of increasing the octane content of gasoline: increasing the volume of gasoline aromatics or increasing the volume of ethanol.
While ethanol has a higher volatility than gasoline, meaning it vaporizes more quickly, it is a cleaner-burning alternative to petroleum-based octane boosters. Additionally, the toxicity of ethanol is low compared to the health effects of BTEX and its combustion products, such as ultrafine particulates UFPs and polycyclic aromatic hydrocarbons PAHs.
A modest increase of ethanol content in fuel from 10 to 15 percent would result in an anticipated 6. There is contradictory evidence that increasing ethanol content in gasoline increases nitrous oxide NOX emissions, an ozone precursor.
Huff, L. Moore, M. DeBusk, and S. Department of Energy and the U. Environmental Protection Agency. DOE and the U. Toggle navigation. Selling your car? We can help you advertise its mpg. Vehicles produce about half of the greenhouse gases from a typical U. We can help you calculate and track your fuel economy. MPG estimates from drivers like you! Answers to frequently asked questions about octane. Enter vehicle or phrase. Selecting the Right Octane Fuel What is octane rating?
What octane fuel should I use in my vehicle? Why do some manufacturers require or recommend the use of higher octane gasoline? What if I use a lower octane fuel than required for my vehicle?
Will using a higher octane fuel than required improve fuel economy or performance? Why does higher octane fuel cost more?
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