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Difference between Leaded Petrol and Unleaded Petrol

Difference between Leaded Petrol and Unleaded Petrol


Leaded petrol and unleaded petrol are two types of fuel that can be used in cars. Both have their pros and cons, but what is the key difference between them? Leaded petrol contains lead in its fuel mixture, whereas unleaded petrol does not. This is why leaded petrol is often referred to as “traditional” petrol – it has been around for many years. Unleaded petrol is a newer type of fuel that was created to try and reduce environmental pollution. Lead can cause serious health problems, so by removing it from the fuel mixture, unleaded petrol is a more environmentally friendly option. However, it can also be more expensive to run your car on unleaded fuel than on led.

What is Leaded Petrol?

Leaded petrol, also known as leaded gasoline, is a type of fuel that contains lead additives. These additives help to improve the performance of the gasoline and reduce engine knock.

  • However, leaded petrol also releases harmful emissions into the environment, including lead particles and other air pollutants. As a result, its use is now restricted in many countries.
  • Leaded petrol was first developed in the 1920s and quickly became the standard for gasoline. However, the health effects of lead exposure were not well understood at that time.
  • It was not until the 1970s and 1980s that researchers began to realize the harmful impacts of leaded petrol on human health. As a result, many countries have now banned or phased out its use. Leaded petrol is still used in some parts of the world, but its days are numbered.

What is Unleaded Petrol?

Unleaded petrol, also known as gasohol, is a mixture of gasoline and ethanol. It was first introduced in the early 1980s as a way to reduce air pollution from engine exhaust.

  • Unleaded petrol typically contains 10% ethanol, but the exact composition can vary depending on the country. In the United States, for example, unleaded petrol must contain at least 9% ethanol.
  • Unleaded petrol is also used in some racing cars because it provides a higher octane rating than gasoline alone. This higher octane rating helps to prevent engine knock, which can damage engines.
  • Unleaded petrol is also less likely to cause corrosion than gasoline. As a result, it is often the preferred choice for vehicles with aluminum engines.

Difference between Leaded Petrol and Unleaded Petrol

  • Leaded petrol was once the most common type of fuel for road vehicles. It contained a chemical additive called tetraethyl lead, which acted as an antiknock agent, preventing engine knocking and pre-ignition.
  • However, it was later discovered that lead is a toxic substance, and its use in petrol was phased out in most countries from the 1970s onwards. Unleaded petrol, which contains no lead, is now the most widely used type of fuel.
  • It offers a number of benefits over leaded petrol, including reduced emissions of harmful substances such as carbon monoxide and nitrogen oxides. In addition, it helps to protect engine components from wear and tear, prolonging the life of the engine. As a result, unleaded petrol is now the preferred choice for most motorists.


In the United States, unleaded gasoline is the standard for vehicles. Leaded gasoline was phased out in 1986 because it damages engines and pollutes the air. The main difference between leaded and unleaded petrol is that leaded petrol contains tetraethyl lead which helps to keep the engine clean and running smoothly. Unleaded petrol does not contain this additive, so it can cause problems with a car’s ignition system and spark plugs if used over an extended period of time.

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