What makes octane

You should always use at least the minimum octane rating recommended by your vehicle manufacturer. Using a lower-octane fuel than required can cause knocking and will prevent your vehicle from meeting its stated fuel economy. Higher-octane fuels can potentially increase performance in some vehicles when towing heavy loads, especially in hot summer weather. With a multifunctional, industry-leading additives package that comes standard in every grade, Cenex gasoline gives you worry-free, fuel-efficient miles on the road.

Now who wants to ride shotgun? Spread The Word. Lead is still used in some aviation fuels. Thanks to coordinated efforts, lead is now absent from gasoline in most of the world. Following the lead phase-out in the United States, the oil refining industry chose to construct additional refining capacity to produce octane from other petroleum products, rather than from renewable sources such as ethanol.

RFG has an increased oxygenate content, which helps it burn more completely. As a result, RFG lowers the formation of ozone precursors and other air toxics during combustion. Petroleum refiners were not required to use any particular oxygenate in RFG, but by the late s, a petroleum product, methyl tertiary butyl ether MTBE , was used in 87 percent of RFG due to its ease of transport and blending.

In the Midwest, ethanol was a more common component of RFG. Despite its success at reducing ozone precursors, MTBE was phased out of the gasoline pool due to concerns over its solubility in water, which resulted in the contamination of water resources in numerous states. Currently, 30 percent of gasoline sold in the United States is reformulated gasoline.

Ethanol is providing the additional octane required by RFG. At the time, the U. At the same time, EPA and the U. The BTEX complex is a hydrocarbon mixture of benzene, toluene, xylene and ethyl-benzene.

Commonly referred to as gasoline aromatics, these compounds are refined from low-octane petroleum products into a high-octane gasoline additive. While some volume of BTEX is native to gasoline, it is also added to finished gasoline to boost its octane rating. The total volume of BTEX aromatics in finished gasoline depends on the desired octane value and other desired fuel properties.

When faced with the removal of lead as the primary octane provider in gasoline, refiners had two available alternatives, BTEX and ethanol. The refining industry invested in additional refining capacity to replace lead with BTEX, a high-octane petroleum refining product. As a result of its substitution for lead, BTEX volume rose from 22 percent to roughly a third of the gasoline pool by In premium gasoline grades, the BTEX volume content was as high as 50 percent.

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.

Inside an engine, you have the piston moving up and down, with the injectors metering a given amount of fuel into the combustion chamber as the piston travels up toward top-dead-center position.

As it moves up, it compresses the fuel-air mix already in the cylinder. When the air fuel mixture ignites by the heat of compression rather than because of the spark from the spark plug, it causes knocking in the engine and a loss of power.

The knocking sound is caused by two exploding "flame fronts" - one explosion from the pre-ignition of the fuel-air mix caused by compression and the other from the rest of the fuel-air being ignited at a slightly different time by the spark plug. The two flame front explode and send shock waves through the air of the cylinder, which meet in the combustion chamber and give you that annoying knock effect.

Lower octane gasoline like "regular" octane gasoline can handle the least amount of compression before igniting. The compression ratio of your engine determines the octane rating of the gas you must use in the car. This is the same as saying your engine is designed to perform its best with a specific octane rating of gasoline.

A "high-performance engine" has a higher compression ratio and requires higher-octane fuel to prevent it from prematurely igniting fuel before the spark plug does it. So, octane does not enhance the explosion in the cylinder like most people think.

What does octane do? It just prevents the air-fuel mixture from igniting before the spark plug does it. Firing the air-fuel mixture at the proper time gives you the maximum power your engine was designed to get. Using higher-octane gasoline than your engine is designed to utilize is only wasting your money.