Leaded vs Unleaded Gas: Differences, Major Grades, Best Use

What brands of unleaded gasoline do you know? And what is its difference from ethylated? The latter, by the way, has been banned in almost all countries of the world.

Leaded and unleaded gasoline are the two main types of gasoline used in automobiles. Leaded gasoline contains an additive called tetraethyl lead, which is used to boost octane ratings and reduce engine knock. Unleaded gasoline, on the other hand, does not contain this additive.

Leaded vs Unleaded Gas: Differences, Major Grades, Best Use

What is unleaded gasoline?

Unleaded gasoline is a fuel that is made from petroleum by distilling it into different compositions. The resulting gasoline mixture has high detonation characteristics during compression. A critical compression level provokes self-ignition before a spark from the spark plug occurs. In other words, detonation occurs too early, which increases the wear of pistons and cylinders, loads the connecting rod and piston group, and leads to an increase in temperatures, due to which the engine overheats.

The parameter that determines the degree of compression at which detonation occurs is called the octane number. Gasoline obtained immediately after oil refining has an octane rating of 56-60. Such fuel is unsuitable for a car.

The addition of special environmentally friendly additives from alcohols and ethers to the fuel helps to increase this indicator. Such gasoline is called unleaded. It is safe for the environment and humans practically does not clog the car catalyst, and is actively used all over the world.

Unleaded fuel comes in various grades, depending on the octane number.

What is leaded gasoline?

Leaded gasoline is, in fact, the same fuel obtained by distilling oil. However, the desired octane number was achieved here by adding tetraethyl lead. This additive makes the fuel toxic. Its exhaust contains too much volatile lead, which, settling in the lungs of a person, leads to serious illness. The component also harms plants, and animals, and heavily pollutes the atmosphere. Also, different brands of leaded gasoline have a detrimental effect on the internal units of the car. In particular, on the engine, exhaust system, and catalyst.

For the first time, ethyl impurities in gasoline mixtures began to be added in the 20s of the last century at General Motors. The fact of toxicity of leaded gasoline was carefully hushed up. For a long time, they did not talk about its toxicity, but after several decades, the truth triumphed. Closer to 80m, such brands disappeared from the shelves of American gas stations. By the 2000s, this happened in Europe as well.

Let’s summarize! Unleaded gasoline does not contain tetraethyl lead additives. Alcohol and ethereal additives that do not destroy the environment are introduced into it. Conversely, leaded contains ethyl metal-containing mixtures, due to which toxic lead is present in the exhaust. Such stamps are now banned.

Leaded vs unleaded gas grades

Major unleaded Gas grades

Consider what brands of unleaded gasoline exist:

  1. AI 80;
  2. AI 92;
  3. AI 95;
  4. AI 98.

A group of letters indicates that the octane number was selected by the research method. The numbers express the detonation resistance of the brand.

Also, this Standard identifies several environmental classes of unleaded fuel:

  • K2;
  • K3;
  • K4;
  • K5;
  • K6

The environmental class determines the level of sulfur and other harmful substances in the exhaust. The higher the class, the cleaner the fuel. For example, eco class K5, in the same volume of the gas cloud, implies 50 times less sulfur than K2. In unleaded fuel K6, sulfur is completely absent. Currently, it is prohibited to produce non-environmentally friendly fuel with a class below K5 in the territory of the countries that are members of the Customs Union. Branded gas stations from well-known gasoline manufacturers adhere to these standards. But small private networks, as well as some manufacturers from Central Asia, are still “hacking”.

Remember, when refueling, you have every right to request documents for the fuel poured into the tank. In the technical documentation of any gas station, each brand is indicated by the following analogy: unleaded gasoline brand AI 92 K5.

Main leaded Gas grades

As we mentioned above, such fuel is prohibited in our country. What brands of his were in use before the ban?

  • AI 93;
  • A 66;
  • A 76.

The letter A in the designation indicates that the octane number is determined by the motor method.

The indicated brands of leaded gasoline in the Soviet Union were necessarily subject to tinting (for example, leaded gasoline of grade A 76 was green, AI 93 was blue). So drivers could identify the fuel without additional research.

Dyes did not affect the quality of the fuel.

Leaded and unleaded gasoline: the difference

Additives with an alcohol or ester base have not always been used for cars. For 80 years, since the 1920s, the most common component for increasing the antiknock properties of gasoline has been tetraethyl lead.

Leaded and unleaded gasoline: the difference

The organic compound of metal and carbon has the formula Pb (CH 3 CH 2 ) 4  and is obtained by synthesizing chloroethane with PbNa, a compound of sodium and lead. The substance is in a liquid state and has high volatility. Gasoline, in which TPP is added as an additive, is called leaded.

Tetraethyl lead does increase octane significantly and is cheap and readily available. However, the compound has serious drawbacks related to the characteristics of lead. Gasoline with this additive significantly wears out the engine, contaminating the internal parts of the crank mechanism and fuel lines (which ultimately leads to excessive fuel consumption).

The additive has toxic and toxic properties – liquid vapor enters the lungs of a person through the respiratory system, causing severe and life-threatening poisoning. The molecules of the mixture can enter the body even through the skin, depressing the central nervous system and in many cases leading to irreversible consequences. And given that the saturation vapor pressure of tetraethyl lead remains high even at zero temperature, the additive is finally banned in most countries today.

Unleaded gasoline is fortified with additives that are free of lead and its compounds. Among the common additives, one can note methyl tert-butyl ether, which has practically no negative effect on the operation of the motor, and N-methyl aniline, an additive, although it contributes to the formation of a resin layer on parts, quite effectively increases the octane number. But the main property of unleaded gasoline additives is safety for both humans and cars.

By the way, we recall that gasoline is used not only for refueling cars but also for powering large units for various purposes. For example, in a dental laboratory, only unleaded gasoline is allowed, as it is not poisonous.

How can you tell unleaded gasoline from lead-containing gasoline? 

By the appearance and smell of the liquid, this is impossible to do. Therefore, if you have concerns about the honesty of a regular supplier of fuel for your car, then you can send a fuel sample to the laboratory for analysis. And it’s better to choose trusted gas station chains and private suppliers who participate in transport card programs for refueling.

what color is unleaded or leaded gasoline?

Today, unleaded gasoline is not tinted, and therefore, it is problematic to determine the brand by color. How to understand whether this fuel is leaded or unleaded. Neither the smell nor the consistency will also help to draw an accurate conclusion. Unless, ethyl gives the fuel a fat content, but it is impossible to judge by this sign for sure.

In view of the existing ban, of course, you will be assured that the fuel does not contain toxic metal additives. However, only laboratory analysis will help to verify this for sure.

To protect yourself from low-quality manufacturers and sellers, refuel only at certified gas stations of famous brands. Most of them can already be seen on the maps of 

If you suspect something is wrong, check the spark plugs. Even one consumption of a full tank of leaded fuel is enough for a reddish coating to appear on these elements.

Should I use regular or unleaded gasoline?

If you carefully read the article, you should have removed this issue from the agenda. With regard to leaded, and even more so. Its extremely negative impact on the environment, as well as on the state of the catalyst and the car engine, is obvious and very convincing.

Refuel at trusted gas stations and don’t be fooled by the low prices of unfamiliar gas stations! Health to you and your wheelbarrow!

can you mix leaded and unleaded gas?

Yes, you can mix leaded and unleaded gasoline, but it is not recommended. Leaded gasoline contains an additive called tetraethyl lead, which is harmful to the environment and can damage the emission control systems in newer vehicles.

Unleaded gasoline does not contain this additive. Mixing the two types of gasoline can also negatively impact the performance of your engine. It is best to use the type of gasoline recommended by the manufacturer of your vehicle.

which is cheaper leaded or unleaded petrol

It is difficult to make a general statement about whether leaded or unleaded gasoline is cheaper as the price of gasoline can vary greatly depending on location, taxes, and market conditions. In most places, unleaded gasoline is cheaper than leaded gasoline, but this is not always the case. It’s best to check the prices at local gas stations to see which type of gasoline is more cost-effective for you.

It’s important to note that in most countries, leaded gasoline is banned for road usage and it’s not available for sale as leaded gasoline is not environment-friendly and also it can cause health hazards.

is my car leaded or unleaded?

The best way to determine if your car requires leaded or unleaded gasoline is to consult the owner’s manual or check the vehicle’s fuel filler cap or door. It should have a label that indicates the recommended fuel type.

If you don’t have the manual or the label is not clear, you can check the model and make of your car online, most of the vehicle’s manufacturers have a list of their vehicles and the type of fuel they use on their websites.

As a general rule of thumb, vehicles manufactured before the 1980s are more likely to require leaded gasoline, while vehicles manufactured after that time are designed to run on unleaded gasoline. However, it’s always best to check the manual or the label to be sure.

It’s also worth noting that some countries have banned the use of leaded gasoline for road usage, if you are living in such country, the gasoline stations will only sell unleaded gasoline.

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