Unleaded and Leaded Fuel
what are the advantages and disadvantages of leaded and
I hear that they are changing from leaded fuel to unlead, why? What is the
The Unites States and most other countries switched from leaded to unleaded
fuel years ago. The lead additive, tetraethyllead, retarded "preignition"
in gasoline engines. Preignition causes engines to run rough, and to not
shut off when the key is turned off. The suppression of preignition is
measured by the gasoline's "octane rating". A good high-octane gasoline
allows a standard engine to run smoothly. Leaded gasoline also protected
some older car engines from wearing down by covering soft engine parts with
There are two major problems with using leaded fuel.
1) Lead is extremely
toxic, and causes mental retardation in children. Lead oxide from car
exhaust accumulates in soil near roads, and children can get it on their
hands from playing outside. They then ingest it, and it causes its damage.
2) Leaded gasoline ruins automobile catalytic converters. As a result of
these two problems, lead in gasoline has been banned in the U.S. Other
additives, such as methyl-tert-butyl ether (which is about to be banned),
had to be used to improve gasoline's octane rating.
Richard E. Barrans Jr., Ph.D.
PG Research Foundation, Darien, Illinois
Do not know from where you are writing your question, but in this country
(USA) we changed from leaded to unleaded fuel a long time ago. Leaded
gasoline may have higher octane ratings which factors into the power output
of a car engine, its efficiency, etc., but the lead also comes out in the
combustion products in the exhaust and lead is a toxic material to humans
over a long period of time when inhaled or ingested.
I believe there is a study in the USA done by either the U.S. EPA or the
National Institutes of Health that shows housing areas closer to major
expressways or in cities where the housing areas are close to major
thoroughfares have elevated levels of lead in the soil surrounding the homes
due to vehicle emissions over a long period of time. Lead has particularly
disastrous health effects on young children's growth and mental faculties,
as I understand it (I am not a health physicist or industrial hygienist).
You can find more information in regard to lead's properties in fuel by
consulting a text book dealing with automotive engine performance and fuel
effects, by consulting a major oil company like BP-Amoco or ExxonMobil, etc.
or via other sources. You can find more information on lead's effects on
humans by consulting some reference material on the subject of toxicology
and hazardous environmental elements. I am not an expert in this area, and
I wish I could steer you to something more specific but this is the best
short answer I can give you at present.
Leaded fuels were phased out in the United States several
years ago. It was concluded that some of the lead in water and in the soil
was from precipitation runoff of lead off of the roads and
the soil along roads. Since lead can cause problems in our brains,
including mental retardation (usually the result of children eating lead
paint), as well as similar bad effects on animals and plants in the
environment, it is best to eliminate the use of lead wherever possible. In
the Department of Energy, where I work, we have also tried to eliminate as
much solid lead as possible, since the outside of solid lead oxidizes; this
oxidation can penetrate the skin and get into the blood. Obviously, this is
Lead was used in fuels as a lubricant and octane (energy level) booster.
However, we have developed other less dangerous chemicals to use in it's
place in fuels. Gasoline still includes a tiny amount of lead because of
the natural processes under which oil formed in the ground, but we no longer
add lead to fuels in the United States.
Lead has not been in gasolines for use for years mainly because lead
pollution affects living cells and health, especially in children. Lead
was added to gasoline as a liner for cylinder walls in a compression
engine to smooth the effects of metal rubbing metal. It is abundant and
cheap. Now other chemicals are used.
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Update: June 2012