Different Types Of Gasoline For Engines


There are many options for classifying gasoline. Fuel is divided into types according to a variety of indicators.

Next, the main options, the principles by which the separation occurs, as well as related issues will be considered.

Types of gasoline for engines

Requirements for the quality of gasoline

Gasoline for the car engine must:

  • Enter the power supply system of the machine without interruption;
  • Ensure the desired composition of the air-fuel mixture and its combustion without detonation;
  • Do not cause corrosion;
  • Leave few deposits as possible;
  • Maintain properties during transportation and storage.

The engine will work reliably and for a long time only if high-quality, suitable gasoline is used with it. This implies a number of requirements, for example, to detonation resistance – to increase it, additives are added to the composition.

It is also necessary that the calorific value is sufficiently high. There are also requirements for the content of various kinds of impurities, due to which deposits appear on the exhaust and fuel systems (the fewer there are, the longer the motor will last).

The products of combustion must not be corrosive or toxic. At any operating temperature of the motor, a homogeneous combustible mixture should occur: for this, it is necessary that the volatility is at a sufficient level. In addition to the above, there are other requirements: for example, stability and environmental friendliness – they will be discussed in more detail below.

Types of gasoline for engines by octane number

This classification of gasoline is the most commonly used. It is reflected in the standard marking. So, in AI-92, “A” means “automobile”, “I” – that the octane number was established by the research method, but here 92 is the octane number itself.

The following main types of gasoline are distinguished:

  • AI-98 . Must be used in turbocharged engines, its compression combustion rate is higher than that of the following types – it is 12-14.5.
  • AI-95 . High-quality gasoline. In most cases, there is no point in using the AI-98 instead, except when recommended by the car manufacturer. Compression during combustion – 10-12.5. For the most part, the parameters do not differ from the AI-98. But one should distinguish between ordinary AI-95 and Extra AI-95 – the first contains about a third more lead.
  • AI-92 is widely used due to the fact that it fits most cars, while it costs less than AI-95. Its quality is average. Production was planned to be stopped several times, but this never happened. It still remains one of the main species. Even many foreign cars are tuned to work on it.

These are descriptions of familiar types of gasoline – they are the most common at gas stations.

But the classification of gasoline into classes based on the octane number is not limited to the listed options, there are others.

For example, A-76 is low-quality gasoline, most often it is used for agricultural vehicles.

Recently, the AI-100 has appeared on sale, suitable for forced engines, it allows you to use their power more efficiently, while its consumption is lower. Some species are practically not produced at all. For example, the equipment working on the A-72 is almost no longer used.

It is worth noting: if gasoline is labeled as “A” instead of “AI”, this means that a motor method was used to determine the octane number – it gives numbers below the research one.

Just as it usually makes little sense to fill the tank with more expensive gasoline than the one recommended by the manufacturer, so you should not use cheaper brands on an ongoing basis.

If all systems are designed for AI-95, then replacement with AI-92 can cause a variety of phenomena: for example, increased fuel consumption and accelerated destruction of individual elements.

By the way, you can also trade gasoline on the stock exchange, through futures. Everyone can do this since the minimum deposit with brokers is a symbolic $100.

Types of gasoline for engines by the fractional composition

Types of gasoline for engines by the fractional composition

Another classification of motor gasoline. It distinguishes ten classes, and everything can be divided into three categories:

  • classes A and B for summer gasoline;
  • from C to F for winter;
  • from C1 to F1 for off-season.

Class A gasoline has the lowest saturation vapor pressure (VPV), and class F has the highest, respectively.

There are more light fractions in winter gasoline, so butane is specially added to it. As a result, its DNP is higher, and therefore the starting qualities are better – it boils well, which allows you to start the engine without problems in the cold. However, with an increase in DNP, the likelihood of vapor locks increases.

In addition, light fractions tend to volatilize, so if there are a lot of them in gasoline, losses even when stored in a warehouse or directly in the tank will be high. DNP in gasoline intended for use in the warm period (from early April to late September) should not exceed 500 mm Hg (or approximately 67 kPa), and in winter – 700 mm (93 kPa).

Since it is easier to store summer gasoline, it is often used at gas stations in winter. This does not harm the engine, but it should be borne in mind that in the cold on class A or B gasoline, it may simply not start.

Type of gasoline based on Evaporation classification

Evaporation directly depends on what gasoline consists of, that is, its fractional composition. If it is optimal, a uniform mixture with a sufficient concentration of fuel enters the cylinders. If bad, part of the fuel will not burn at all.

The classification of gasoline according to volatility is made depending on the level of DNP and the boiling point. It is set at what temperature a certain percentage of gasoline boils away, in the standard classification it is 10%, 50%, 90%. It also determines how much gasoline boils off at 70 °C.

The classes are called very simply: first, second, and so on up to the fifth. The former has the highest DNP and the lowest boiling point. Further, up to the fifth grade, the first indicator decreases, and the second grows.

The first 10% of the gasoline that boils away are light fractions. It is at their expense that the engine is started. After them, medium ones begin to boil away, making up to 50% of the volume. If their boiling point is too high, the engine will take a long time to warm up, and acceleration will be too slow.

Next, the final fractions come into play: in order for them to boil away, the temperature must rise to about 190 ° C. After that, 90% of the volume of gasoline should be used up. If the temperature at which these fractions evaporate is too high, evaporation may not be complete, resulting in higher fuel consumption and the engine not being able to deliver full power.

In addition, part of the remaining unburned fuel fractions will settle on the cylinder walls and wash the oil off them, the other part will drain into the crankcase, due to which the oil will be diluted and its efficiency will decrease.

To prevent this from happening, the volatility class of the fuel must be selected in accordance with the manufacturer’s recommendations and according to the season.

Environmental classes of gasoline

Another classification of motor gasoline is ecological. According to it, four types are distinguished:

  • K2 – up to 500 mg of sulfur per kg is allowed, as well as up to 1.3% of monomethyl amine (MMA).
  • K3 – up to 150 mg of sulfur per kg and up to 1% MMA, respectively.
  • K4 – up to 50 mg / kg and 1%.
  • K5 – up to 10 mg/kg, MMA should be absent.

This classification of gasoline is valid in most of world. The environmental class can be indicated immediately after the octane number, for example, AI-95-4. But this applies only to gasoline that meets GOST standards. In addition to it, it is also sold according to TU – it does not live up to these standards in some respects.

There is always a risk of stumbling upon surrogate gasoline. According to various estimates, its volume on the market is 20-30%. It does not comply with any environmental standards, it can be dangerous not only for the environment in the long term but also for the car owner himself in the near future. It is worth noting which types of gasoline are surrogates most often: this is AI-92 and, to a lesser extent, AI-95, most of all fakes are among diesel fuel.

You can often find other designations of the environmental class: Euro-2, Euro-3, and so on. This is a European version of the marking. Environmental classes were introduced gradually: for example, Euro-1 appeared in 1992 and is no longer used; Euro-2 was approved in 1995, and the requirements for carbon monoxide emissions became three times tougher.

In Euro 5 and Euro 6, the carbon emission standards have not changed compared to the previous standard, but the requirements for the emission of other harmful substances have become tougher. The environmental class of gasoline must correspond to that of the car or be higher.

What type of compound is gasoline?

While additives may not seem like a big deal by volume, they do have a significant impact on the properties of gasoline. They are used for:

  • increase resistance to detonation;
  • reduce engine overheating;
  • reducing the number of deposits remaining from the fuel;
  • reducing the level of carbon deposits in the exhaust system and combustion chamber;
  • increasing the degree of evaporation;
  • reducing the content of benzene and sulfur in the exhaust gas.

There are a lot of additives. Fuel manufacturers are in every possible way sophisticated with the selection and dosage of the components of which they are composed. Each well-known manufacturer strives to present its composition as special and most effective; This can be done primarily through additives.

With all the variety by purpose, they can be divided into several main categories:

  • starting – increase the volatility of gasoline;
  • friction modifiers – thanks to the film on the surface of rubbing pairs, they reduce their wear;
  • running-in – improve rubbing, useful after repair;
  • corrosion inhibitors – protect the oxidized metal from destruction;
  • stabilizing – do not allow the fuel to oxidize during storage;
  • catalyzing – activate combustion and reduce soot;
  • cleaning – clean the fuel system from deposits;
  • dryers – remove excess moisture, both contained in the fuel itself, if its quality is not high enough, and condensate from the surface of the tank;
  • octane correctors – increase the octane number and prevent detonation.

Not all additives are equally useful. Substances contained in them can be harmful and toxic. Some of them have become obsolete or even banned, while others are still used. Here are some of these substances:

Tetraethyl lead. Allows you to increase power, at the same time makes the motor less noisy and reduces smoke. With it, the quality of the fuel increases: its resistance to self-ignition becomes higher, and detonation is lower. The substance is very toxic, easily seeps into any openings. It poisons even when touched, so there is a considerable risk when using gasoline with it.

Manganese increases the class, but its use leads to premature failure of the candles and converter.

Additives aimed at increasing the octane number:

  1. Naphthalene – with it, there are more harmful emissions, including those contributing to oncological diseases. In addition, because of it, a crystalline precipitate clogs the filters.
  2. With ethanol, the efficiency of the motor increases, and fuel burns better. But it corrodes gaskets and shortens the life of the motor, and if the dosage is exceeded, detonation will appear.
  3. Acetone makes the exhaust more toxic, and at high dosages, it greatly lowers the octane number.
  4. Aromatic carbohydrates, like toluene and benzene, give an increase of up to 10 units, but gradually corrode the elastic parts, which leads to increased corrosion.

Most of these additives are either not used at all by fuel manufacturers or are used with strict restrictions, but they can be found in high quantities in counterfeit gasoline. Sometimes car owners add them themselves, wanting to improve the efficiency of low-quality gasoline.

With the listed additives, you should be especially careful, and even more so, not add a lot at once. With an excessive increase in the electrical conductivity of gasoline, problems are possible up to spontaneous combustion.

Regular gasoline in good condition may be almost colorless, bluish, or yellowish, but it should not be pronounced. If it is reddish, this may indicate that metal-containing additives have been introduced into it. If it has an excessive amount of octane boosters, it can be bright yellow and smell strong, and the smell can also give you a headache.

Such oil still loses to pure “synthetics”, but, unlike mineral oil, which is rarely used in modern engines, it is used everywhere.


The classification of engine gasoline is rather complicated since it can be based on different parameters and properties. In addition, it is constantly changing and supplementing along with the development of industry and the emergence of new technologies, on the one hand, and the tightening of environmental requirements, on the other.

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