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Usage
The U.S. used about 521 billion litres (137 billion gallons) of gasoline in
2006, of which 5.6% was mid-grade and 9.5% was premium grade.
Additives
Gasoline additive
Lead
The mixture known as gasoline, when used in high compression internal combustion
engines, has a tendency to ignite early (pre-ignition or detonation) causing a
damaging "engine knocking" (also called "pinging" or "pinking") noise. Early
research into this effect was led by A.H. Gibson and Harry Ricardo in England
and Thomas Midgley and Thomas Boyd in the United States. The discovery that lead
additives modified this behavior led to the widespread adoption of the practice
in the 1920s and therefore more powerful higher compression engines. The most
popular additive was tetra-ethyl lead. However, with the discovery of the
environmental and health damage caused by the lead, and the incompatibility of
lead with catalytic converters found on virtually all US automobiles since 1975,
this practice began to wane in the 1980s. Most countries are phasing out leaded
fuel; different additives have replaced the lead compounds. The most popular
additives include aromatic hydrocarbons, ethers and alcohol (usually ethanol or
methanol).
In the U.S., where lead was blended with gasoline (primarily to boost octane
levels) since the early 1920s, standards to phase out leaded gasoline were first
implemented in 1973. In 1995, leaded fuel accounted for only 0.6 % of total
gasoline sales and less than 2,000 tons of lead per year. From January 1, 1996,
the Clean Air Act banned the sale of leaded fuel for use in on-road vehicles.
Possession and use of leaded gasoline in a regular on-road vehicle now carries a
maximum $10,000 fine in the United States. However, fuel containing lead may
continue to be sold for off-road uses, including aircraft, racing cars, farm
equipment, and marine engines until 2008 . The ban on leaded gasoline led to
thousands of tons of lead not being released in the air by automobiles. Similar
bans in other countries have resulted in lowering levels of lead in people's
bloodstreams. .
A side effect of the lead additives was protection of the valve seats from
erosion. Many classic cars' engines have needed modification to use lead-free
fuels since leaded fuels became unavailable. However, "Lead substitute" products
are also produced and can sometimes be found at auto parts stores.
Gasoline, as delivered at the pump, also contains additives to reduce internal
engine carbon buildups, improve combustion, and to allow easier starting in cold
climates.
In some parts of South America, Asia, Europe and the Middle East, leaded
gasoline is still in use. Leaded gasoline was phased out in sub-Saharan Africa
with effect from 1 January 2006. A growing number of countries have drawn up
plans to ban leaded gasoline in the near future.
MMT
Methylcyclopentadienyl manganese tricarbonyl (MMT) has been used for many years
in Canada and recently in Australia to boost octane. It also helps old cars
designed for leaded fuel run on unleaded fuel without need for additives to
prevent valve problems.
US Federal sources state that MMT is suspected to be a powerful neurotoxin and
respiratory toxin, and a large Canadian study concluded that MMT impairs the
effectiveness of automobile emission controls and increases pollution from motor
vehicles.
In 1977, use of MMT was banned in the US by the Clean Air Act until the Ethyl
Corporation could prove that the additive would not lead to failure of new car
emissions-control systems. As a result of this ruling, the Ethyl Corporation
began a legal battle with the EPA, presenting evidence that MMT was harmless to
automobile emissions-control systems. In 1995, the U.S. Court of Appeals ruled
that the EPA had exceeded its authority and, as a result, MMT became a legal
fuel additive in the US. MMT is nowadays manufactured by the Afton Chemical
Corporation division of Newmarket Corporation .
Ethanol
In the United States, ethanol is sometimes added to gasoline but sold without an
indication that it is a component. Chevron, 76, Shell, and several other brands
market ethanol-gasoline blends.
In several states, ethanol is added by law to a minimum level which is currently
5.9%. Most fuel pumps display a sticker stating that the fuel may contain up to
10% ethanol, an intentional disparity which allows the minimum level to be
raised over time without requiring modification of the literature/labeling. The
bill which was being debated at the time the disclosure of the presence of
ethanol in the fuel was mandated has recently passed. This law (Energy Bill
2005) will require all auto fuel to contain at least 10% ethanol. Many call this
fuel mix gasohol.
Dye
M Fuel dyes
In the United States the most commonly used aircraft gasoline, avgas, or
aviation gas, is known as 100LL (100 octane, low lead) and is dyed blue. Red dye
has been used for identifying untaxed (non-highway use) agricultural diesel. The
UK uses red dye to differentiate between regular diesel fuel, (often referred to
as DERV), which is undyed, and diesel intended for agricultural and construction
vehicles like excavators and bulldozers. Red diesel is still occasionally used
on HGVs which use a separate engine to power a loader crane. This is a declining
practice however, as many loader cranes are powered directly by the tractor
unit.
Oxygenate blending
Oxygenate blending adds oxygen to the fuel in oxygen-bearing compounds such as
MTBE, ETBE and ethanol, and so reduces the amount of carbon monoxide and
unburned fuel in the exhaust gas, thus reducing smog. In many areas throughout
the US oxygenate blending is mandated by EPA regulations to reduce smog and
other airborn polutants. For example, in Southern California, fuel must contain
2% oxygen by weight, resulting in a mixture of 5.6% ethanol in gasoline. The
resulting fuel is often known as reformulated gasoline (RFG) or oxygenated
gasoline. The federal requirement that RFG contain oxygen was dropped May 6,
2006 because the industry had developed VOC-controlled RFG that did not need
additional oxygen.
MTBE use is being phased out in some states due to issues with contamination of
ground water. In some places it is already banned. Ethanol and to a lesser
extent the ethanol derived ETBE are a common replacements. Especially since
ethanol derived from biomatter such as corn, sugar cane or grain is frequent,
this will often be referred to as bio-ethanol. A common ethanol-gasoline mix of
10% ethanol mixed with gasoline is called gasohol or E10, and an
ethanol-gasoline mix of 85% ethanol mixed with gasoline is called E85. The most
extensive use of ethanol takes place in Brazil, where the ethanol is derived
from sugarcane. Over 3,400 million US gallons (13,000,000 m3) of ethanol mostly
produced from corn was produced in the United States in 2004 for fuel use, and
E85 is slowly becoming available in much of the United States. Unfortunately
many of the relatively few stations vending E85 are not open to the general
public. The use of bioethanol, either directly or indirectly by conversion of
such ethanol to bio-ETBE, is encouraged by the European Union Directive on the
Promotion of the use of biofuels and other renewable fuels for transport.
However since producing bio-ethanol from fermented sugars and starches involves
distillation, ordinary people in much of Europe cannot ferment and distill their
own bio-ethanol at present (unlike in the US where getting a BATF distillation
permit has been easy since the 1973 oil crisis.)
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