What is the difference between gasoline and diesel engines: pros and cons

Stages of gasoline production

Gasoline is produced by fractional distillation of crude oil. In the distillation column, the liquid is exposed to high temperatures. As a result, substances that are lighter evaporate and flow upward, from where they are pumped out through special outlet pipes. The separated fraction is treated with catalysts, acids and adsorbents, which help clean the fuel from heavy and harmful impurities.

At the last stage of production, additives are added to the finished fuel to regulate its ignition rate.

This prevents damage to the motor and accidents when working with liquid.

The quality of gasoline fuel can be determined by checking the octane number.

What is diesel fuel

Diesel fuel (DF) belongs to the middle fractions of oil. It consists of alkane compounds containing 13-19 hydrocarbon groups. In everyday life, the word “diesel fuel” is common, which is considered synonymous with diesel fuel, but these 2 types of fuel differ in density, viscosity and boiling point.

DF consists of gas oils. To improve the quality of the mixture, lighter kerosene fractions can be added to it. Their share in fuel reaches 20%.

A feature of diesel fuel is a sharp change in fluidity with decreasing temperature. When using diesel fuel, it is necessary to fill in a grade that corresponds to the climatic conditions of the region.

Diesel fuel: types, properties, application, grades

Diesel fuel: types, properties, application, grades

Diesel fuel is a product of petroleum distillation, consisting of hydrocarbons with a high boiling point from 200 to 350 C. A transparent and slightly viscous liquid of various shades of yellow-brown color. It is used as the main type of fuel for diesel engines and gas diesel engines.

Usage

Improving the quality of diesel fuel allows us to expand the scope of its use every year.

Almost all modern freight transport runs on diesel fuel: trucks, diesel locomotives, sea and river ships, military equipment and agricultural equipment, stationary and mobile power plants, autonomous heating systems with diesel electric generators. Passenger cars with diesel engines are also known in Europe. Studies have shown that fuel savings are about 40% and the safety of exhaust gases is much higher.

Properties

• The flammability of a fuel is the time that elapses between the fuel entering the cylinder and the start of its combustion. The shorter this period of time, the shorter the duration of engine warm-up. Determined by cetane number. If it exceeds 55, the smokiness of the exhaust gases increases greatly.
• Viscosity depends on the presence of paraffin in the raw material. The higher the temperature, the lower the viscosity. The lubricating characteristics of diesel fuel depend on it.

Density. This is the ability of a substance not to mix with water. The higher the density, the more energy is produced during combustion. Sulfur content. The more sulfur, the less corrosion resistance of the entire fuel system. The filterability temperature is the temperature at which the fuel either does not pass at all or passes through the filter very slowly.

Diesel fuel classes

Since 2015, diesel fuel, in accordance with the European standard, has been divided into environmental classes, which depend on its sulfur content. K3, K4 and K5 are isolated, respectively, the amount of sulfur in them should not exceed 350, 50 and 10 mg/kg. If the amount of sulfur exceeds the maximum permissible amount, such diesel fuel is not recommended for use, because environmental pollution increases, wear and tear of the entire fuel system accelerates.

Diesel fuel brands

Based on their performance characteristics, there are four types, which are named by capital letters of the alphabet:

• Summer (L), it includes fuel grades A, B, C, D with a maximum filterability temperature from +5 to -10 ° C. This diesel fuel cannot be used at temperatures below 0°C.

Interseasonal (E), which includes varieties E and F, with a filterability temperature of up to -20°C, is used in spring and autumn. Winter (Z) - with a filterability temperature from -20 to -38°C and is used at an air temperature not lower than -20°C. Arctic (A) - with a maximum filterability temperature of 44°C and an ambient temperature of up to minus 50°C.

Recently, the scope of use of diesel fuel has been expanding, its quality is improving, new sources of production are appearing, and therefore new brands.

How petrol and diesel engines work

Gasoline and diesel engines are internal combustion engines. In an internal combustion engine running on light oil, the fuel-air mixture is formed in a manifold, which is located directly in front of the cylinder. At the final point of compression, fuel vapors combine with air and are evenly distributed throughout the volume of the cavity. The temperature of the mixture at maximum pressure is +500°C. It is ignited by a spark from the spark plug.

In a diesel engine, air compression occurs directly in the cylinders. The gas pressure is 30-50 atmospheres, so spare parts are made more durable and heavier. Due to strong compression, the air temperature rises to +900°C. At the final point of the process, heavy fuel is sprayed from the nozzles.

When interacting with hot gas, its droplets quickly evaporate and a mixture is obtained that is capable of self-ignition. Thus, diesel fuel burns without the participation of spark plugs.

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Key differences between diesel and gasoline engines comparison

Diesel engines, like their close relatives, gasoline engines, have a similar operating principle and are internal combustion engines (ICE). This means that fuel is mixed with air as it enters the engine, and this mixture is compressed inside the engine cylinders. At some point, the fuel ignites (burns), driving the piston and turning the crankshaft, which is connected to the vehicle's transmission, and ultimately turns the wheels. The piston in the cylinder then moves upward, pushing the burnt gases out of the engine and out of the exhaust pipe as exhaust. This cycle repeats several times per second.

The more cylinders an engine has, the smoother it runs and the more power it can produce since combustion cycles occur very close together. However, the more cylinders an engine has, the more complex and mechanically inefficient the engine becomes. Cylinder configuration also affects performance, vibration and other factors. This difference applies to both options.

The main difference between a diesel engine and a gasoline engine is how the fuel is ignited within the mechanism. In a gasoline engine, air and fuel are compressed and at a critical point in the cycle, the spark plug ignites the mixture. But diesel engines don't have spark plugs. When diesel fuel and air are sufficiently compressed, extreme compression generates just the right amount of heat for the mixture to spontaneously ignite. This is called "compression ignition" and is the basis of the engine's operation. When a gasoline engine has compression ignition, we often call it "detonation" and it can ruin the engine. But they are designed to take advantage of this effect.

Because diesel engines use compression ignition, which can quickly destroy a gasoline engine, they are very tough. And they are generally reliable and do not require much maintenance. This used to translate into a tonne of weight, but with modern manufacturing methods the weight penalty has been greatly reduced and the unit's weight is now broadly in line with petrol models.

In addition, a diesel engine is simpler than a gasoline engine because it does not have spark plugs and the electrical system required for them. Cars and SUVs can now run on diesel and have performance more similar to a gasoline engine, but with the increased mileage and reliability of a diesel. In general, diesel will outperform gasoline in the number of kilometers or hours it can run before needing major repairs, so repair bills are lower and generally less frequent for a diesel engine.

What happens if you mix gasoline and diesel?

Mixing 2 types of fuel leads to increased engine wear. If gasoline gets into a diesel engine, the vehicle will quickly stall, because... An ignition spark is required to ignite the mixture. If the car is only partially filled with light fuel, this may not stop the engine, but can lead to overheating of the fuel system and metallic knocking in the engine.

In the opposite situation - diesel fuel gets into the gas tank - the heavy fraction quickly sinks to the bottom and, thus, immediately enters the fuel supply system. The engine loses power and dynamics, and begins to grind and knock. Black smoke comes out of the exhaust pipe. If diesel is the predominant type of fuel, the car will stall within a few minutes, because... the temperature from the compression of the liquid and the spark are not enough to ignite diesel fuel.

When mixing oil fractions, you will need to completely drain the liquid from the tank and flush the supply system with a large amount of the required fuel.

These types can be distinguished by the rate of evaporation and combustion. When immersed, diesel fuel envelops the surface of the object with an oil film that does not disappear over time. In turn, the low-temperature oil fraction quickly forms vapor. Some car enthusiasts also note that gasoline has a stronger odor.

Difference between petrol and diesel engines

Types of internal combustion engines differ in their operating features, power, degree of safety and reliability. Most of these parameters affect the cost of car maintenance and repair.

Exploitation

Differences in the operation of motors are observed in the following aspects:

1. Acceleration depending on crankshaft speed. At minimum speeds, a diesel engine produces much more torque than a gasoline engine. Good traction at idle improves maneuverability on rough roads and off-road conditions. Light fuel engines have a wide range of operating speeds. This results in a gain in speed and less wear on the internal combustion engine when driving fast.
2. Power (number of horsepower). In terms of dynamics, diesel engines are significantly inferior to gasoline models.
3. Resistant to water. Due to the lack of an ignition system, the diesel engine does not suffer from interruptions in high humidity. At the same time, it is more sensitive to water entering the combustion chamber and crankcase.
4. Maintenance. Diesel engines require regular inspection at a service station. The permissible service mileage for them is much less than for gasoline engines. In addition, the owner will have to monitor the condition of the systems more often, change the oil and filters.

Features of operation in the cold season

When choosing fuel, you need to pay attention to its climate type. It reflects the temperature at which the fuel viscosity increases. Summer diesel begins to thicken already at -10...-15°C, so the car will not start in cold weather.

To avoid problems with starting, before the start of the winter season, it is advisable to drain all summer fuel and fill the car with the most liquid and frost-resistant type of diesel fuel - “Arctic”.

After this, you can drive a standard winter diesel engine.

Vibrations and noises

Since heavy engines operate on the principle of compression, noise and vibration on such units will be significantly higher. This disadvantage is compensated for by a more thorough insulation system in the cabin.

Safety

Cars running on diesel fuel are less likely to catch fire during accidents. This is due, first of all, to the slow evaporation of the oily liquid and the absence of high-voltage wires of the ignition system.

Environmental friendliness

The diesel engine has low carbon monoxide (CO) emissions and high nitrogen oxide (NO) and particulate emissions. This is due to the efficient combustion of fuel in the operating cycle.

If previously diesel fuel was considered more environmentally friendly, today strict European standards are demanding for engines of any type.

Diesel engines without reliable exhaust filtration systems or that do not undergo regular maintenance are especially dangerous.

Modern diesel engines are equipped with urea catalysts, which reduce NO to nitrogen, and particulate filters, which purify exhaust gases.

Financial side of the issue

Heavy engines are rarer, so their maintenance and repair are more expensive, and it is more difficult to find a specialist and spare parts for them. The initial cost is also higher than for gasoline-powered cars.

Power and fuel consumption

The advantage of diesel is high torque, relatively fast acceleration and low fuel consumption.

The difference in fuel consumption per 100 km is at least 1.5-2 liters, depending on the total displacement of the internal combustion engine.

In terms of power, in most cases, motors running on low-temperature oil fraction win.

Used cars

Diesel vehicles are more reliable, durable and durable. Purchasing a used car can be a good deal if the buyer is confident in the seller's integrity and regular maintenance.

In addition, diesel-powered vehicles lose less value during operation.

Demanding on fuel quality

Another difference between a diesel engine is its high demands on the composition of the fuel. When using high-quality oil fraction, heavy motors are more durable than light ones, because designed for increased loads. However, irregular maintenance and a large amount of impurities can quickly damage them.

Advantages and disadvantages

The pros and cons of engines using various oil fractions are presented in the table below.

Diesel engine duty cycle

Diesel engine operation diagram

For example, let's take a four-stroke engine (two-stroke systems are not used in modern automotive production). We are not considering a turbine; we will take a high-pressure fuel pump as a diesel injection system.

1. Intake - the piston moves down. the intake valve opens (there may be two of them), fresh cold air saturated with oxygen enters the combustion chamber. Once the piston reaches bottom dead center (BDC), all valves close.
2. Compression - The piston moves upward, compressing the air in a sealed combustion chamber. When compressed. the air becomes very hot, in some cases up to a temperature of 600°C - 700°C. When the piston reaches top dead center (TDC), a dosed injection of diesel fuel occurs using the nozzle. The fundamental issue is the creation of high pressure.
3. Working stroke - Diesel fuel flares up due to air temperature, and intense combustion begins, almost an explosion. The piston moves intensively towards BDC. This cycle characterizes the performance of engines: the crankshaft rotates with high torque, which is typical for a diesel engine.
4. Exhaust - the difference between diesel and gasoline engines in this operating cycle is small. The exhaust valves open and the combustion chamber is cleared of exhaust gases.

What is the fundamental difference? The methods for forming the fuel-air mixture differ. In a diesel engine, fuel is injected into a cylinder already filled with air. The gasoline mixture is formed in the intake manifold and then supplied to the combustion chamber.

Demonstration of diesel engine operation - video

The heavy fuel system operates simply and there are far fewer points of failure. However, the cost of a diesel high-pressure pump offsets the benefits. pic 2

Comparison of gasoline and diesel on different crossover models

Diesel engines are used primarily for SUVs, which have high fuel consumption. In addition to jeeps, there are also several versions of heavy fuel minivans - for example, Citroen Grand C4 Picasso and Volkswagen Caddy.

In most cases, the model is produced in two versions (diesel and gasoline), which allows you to compare the benefits and costs of owning a car.

Citroen Grand C4 Picasso

The minivan from the French manufacturer is available on the Russian market in 3 versions: with gasoline engines of 120 and 150 horsepower (hp) and with a turbodiesel of 115 hp.

With an average cost of gasoline (AI-95) of 44 rubles/l, and diesel fuel - 43 rubles, savings on fuel for every 100 thousand km will amount to 131.7 thousand rubles. Taking into account the higher cost of annual maintenance, the owner will be able to save about 116 thousand rubles.

KIA Sportage

The compact crossover of the South Korean manufacturer is sold in several configurations. The power of a car on light fuel is 150-185 hp, on diesel fuel - 185 hp.

The benefit from owning a KIA Sportage on diesel fuel, taking into account maintenance and refueling, is about 85 thousand rubles.

Hyundai Tucson

The Korean crossover Hyundai Tucson is available with 2 types of engines. In the diesel version, its power is 185 hp, and in the gasoline version - 177 hp.

Savings per 100 thousand km will be no more than 48-50 thousand rubles.

Nissan Qashqai

The popular Japanese-made crossover is equipped with a 130 hp turbodiesel. or one of 2 light fuel engines - 1.2 liters and 115 hp. or 2 liters and 144 hp.

Low fuel consumption will save up to 90 thousand rubles. over 100 thousand km of travel. This offsets the higher purchase and maintenance costs.

Renault Duster

Renault Duster is a popular crossover, which is available in 2 modifications running on gasoline and one diesel version. The power of models with light fuel is 102 and 135 hp, and with heavy fuel - 90 hp.

Savings per 100 thousand km amount to more than 106 thousand rubles.

Nissan X-Trail

The second Japanese crossover is available with a 130 hp turbodiesel. or light fuel engines with 141 hp. and 171 hp

The benefit from owning a car on diesel fuel is more than 100 rubles. for every kilometer of road.

Volkswagen Caddy

The “heeled” minivan is equipped with a 2-liter diesel engine producing 110 hp. or one of the 1.2 liter gasoline engines with a power of 105 and 86 hp.

Thus, diesel is a more profitable type of fuel. However, when repairing and servicing a car over a long mileage, the financial advantage can be compensated at a time.

Diesel engines are more economical

As is already known, the most important and significant advantage of any diesel engine compared to gasoline counterparts is significantly lower fuel consumption. The low consumption of a diesel engine is associated with the peculiarity of converting diesel fuel into energy. For example, a diesel power unit burns fuel more efficiently, which allows it to obtain about 45-50 percent of energy from one volume of burned fuel. The gasoline engine receives approximately 30 percent of the energy. That is, 70 percent of gasoline is burned in vain!!!

In addition, diesel engines have a higher compression ratio than gasoline engines. Since the compression ratio is affected by the ignition time of the fuel, the higher the compression ratio, the greater the engine efficiency.

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Also, modern diesel engines are more efficient due to the absence of a throttle valve on the intake manifold, which is usually used in gasoline cars. This allows diesel engines to avoid the loss of energy associated with the intake of air, which is necessary to ignite the fuel in gasoline engines.

Comparison of gasoline and diesel engines in passenger cars

Heavy engines are rarely installed in passenger cars. This is due to the fact that the benefits of saving fuel on small cars do not compensate for expensive maintenance and problems with finding original spare parts.

Skoda Octavia

The Czech subcompact Skoda Octavia is sold with various engine and drive options. Depending on the year of manufacture, type of fuel and configuration, the machine’s power ranges from 80 to 230 hp.

Savings per 100 thousand km will be no more than 10-20 thousand rubles.

Citroen C4

The Citroen passenger car model is equipped with engines of the same volume.

For 100 thousand km, the owner will be able to save more than 83 thousand rubles on fuel.

Recommendations for selection

Comparing the cost and expenses of a car is a good opportunity to evaluate the advantages and disadvantages of engines in quantitative terms. It is recommended to choose a gasoline model in the following cases:

• for trips within city limits;
• with a small engine volume;
• for driving at high speeds.

Cars with diesel engines can withstand off-road travel better, but the owner will have to more carefully monitor the condition of the fuel filters and undergo maintenance at the frequency recommended by the manufacturer. The higher cost of the car will be paid off by fuel savings in 3-5 years.

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How does a diesel engine differ from a gasoline engine?

The debate between supporters of diesel and gasoline engines has not subsided for a very long time. But you cannot give preference to one device or another - each has its own advantages and, of course, inherent disadvantages of internal combustion engines, and the optimal choice will depend on the specific operating conditions and personal preferences of the owner. Currently, many car manufacturers supply the same models with both petrol and diesel engines, so that there is a choice for adherents of both types of units.

The main differences between diesel and gasoline engines

Principle of operation. To understand how a diesel engine differs from a gasoline engine, first of all, you need to understand the principles of their operation.

1. Gasoline engine. A mixture of air and fuel is formed in the intake manifold, after which it is supplied to the combustion chamber. At the very end of the compression stroke, the final mixing of the air-fuel mixture occurs and its subsequent uniform distribution throughout the entire volume of the cylinder. As a result of compression, the mixture is heated to approximately 500 ° C, after which it is ignited using a candle.

Diesel engine. The formation of the air-fuel mixture in a diesel unit occurs much faster. In the cylinder of a diesel internal combustion engine, only air is compressed, which is heated to 900°C. Fuel is supplied to the chamber separately. Small drops of diesel fuel quickly evaporate and mix with the air. Due to the higher temperature, such a mixture spontaneously ignites and does not require an additional spark.

Power and efficiency. Historically, it has been believed that using diesel fuel is much more economical than gasoline. Now this is only partly true, since the cost of diesel fuel has become almost equal to the cost of gasoline.

However, due to more efficient combustion of the working mixture, fuel consumption in a diesel engine is approximately 15-20% lower. This reading is achieved due to the fact that the degree of compression of the air-fuel mixture in a diesel unit is almost 2 times higher.

Gasoline engines, in turn, have greater performance. For example, the Mercedes-Benz W124 E 200 D in its diesel version has only 75 hp, while its gasoline opponent boasts almost twice as much power, which is 136 hp.

However, it should be noted that the relatively small power of diesel devices is more than compensated by smooth traction at any speed, which is not possible for gasoline engines.

Environmentally friendly. Due to their high environmental friendliness, cars with diesel engines installed in them are in high demand in the USA, as well as in European countries. Exhaust gases from diesel plants emit much less carbon monoxide and other aggressive compounds that cause acid rain and other environmental problems into the air.

The main advantages and disadvantages of gasoline and diesel engines:

The use of diesel engines has a number of advantages:

1. higher efficiency, and, as a result, increased efficiency;
2. the price of fuel is slightly lower;
3. high durability;
4. environmental friendliness;
5. the diesel fuel itself acts as a lubricant;
6. due to the absence of an ignition system, the engine is not afraid of water ingress;

At the same time, diesel plants also have their disadvantages:

1. large engine mass;
2. the fuel system is extremely sensitive to low-quality fuel;
3. maintenance must be carried out more often;
4. a larger capacity battery is required for starting;
5. poor resistance to frost;
6. increased noise and vibration;
7. complexity and high cost of maintenance;
8. cannot tolerate high speeds and speeds.

Like diesel engines, gasoline engines have their advantages:

1. frost resistance;
2. relative cheapness and ease of maintenance;
3. high power;
4. low noise level;
5. not demanding on fuel quality;
6. easily tolerates work at very high speeds.

The disadvantages of gasoline devices include:

1. increased fuel consumption;
2. faster wear;
3. good traction only at certain speeds.

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