Diesel fuel


What are the Standard Diesel Quality Ratings?

What should you look for when choosing diesel fuel? The price, terms of purchase, the supplier's logistics network and reputation, and additional bonuses for wholesale buyers are all important. But the most important thing is diesel quality. It is with quality that you should start looking for a reliable supplier for long-term cooperation. In this article, we will look at how to choose the best diesel fuel. 

What is diesel fuel?

Diesel fuel is a type of petroleum fuel used to drive diesel engines. It is composed primarily of hydrocarbons and is used as an alternative to gasoline in diesel vehicles, agricultural machinery and large industrial equipment.

The main diesel fuel specifications that determine its advantages as a universal fuel resource:

  • Superior calorific value, which means it can provide more energy during combustion than other fuels. In other words, you will need less fuel to produce 1 kW of electricity or a similar amount of heat;
  • Diesel engines are very efficient, which means they can run more economically and use less fuel to do the same amount of work compared to gasoline engines;
  • The use of diesel can help to extend the life of engines due to lower combustion temperatures and less wear and tear on parts. In the long run, this is a significant cost savings;
  • Diesel is less flammable than gasoline, making it less dangerous to store and transport. The lower safety level also simplifies logistics.

Diesel engines operate stably in different climatic conditions and under different loads, which makes diesel fuel profitable for use in many industries and transportation.

How to identify good quality diesel?

Diesel fuel quality can be determined using a number of research and measurement methods. Checking external signs allows you to assess the transparency and purity of the fuel. Odor analysis helps to detect unnatural odors that may indicate contamination. Density tests and calorific value measurements are also important for determining quality. Checking the stability of the fuel during storage complements the analysis.A variety of methods and devices are used to conduct diesel fuel quality tests:

  • Chromatographic - used to analyze the chemical composition. It involves determining specific indicators such as the content of sulfur, aromatic hydrocarbons and other components;
  • Spectroscopy - used to determine the light absorption spectra of diesel fuel, which allows to determine its composition and properties;
  • Gas chromatography-mass spectrometry (GC-MS) - allows to identify and quantify the composition of fuel components, including sulfur, aromatic hydrocarbons, etc;
  • Physical measurements - measuring the density, viscosity, calorific value and other physical properties of the fuel using special devices;
  • Volatility testing - conducted to determine how quickly the fuel evaporates and whether it contains water.

These methods and studies help determine not only the main characteristics of the fuel, but also its impact on the operation and efficiency of vehicles.

Quality characteristics of diesel fuel

Quality indicators include parameters such as density, calorific value and sulfur content. These characteristics are important factors for the efficiency and durability of diesel engines. Let's take a closer look.


Diesel density determines how heavy it is per unit volume, which affects its storage and delivery. It is measured in kilograms per liter or grams per cubic centimeter. The acceptable density range for diesel fuel is 0.82-0.85 kg/l or 820-850 g/cm³. The critical value is above 0.85 kg/l or 850 g/cm³, which may indicate contamination or dilution of the fuel. High density may indicate high quality fuel, as less air can penetrate the system. A low density may indicate contamination or dilution of the fuel, which negatively affects its efficiency.

Point of ignition

The flash point is the temperature at which the fuel vaporizes fast enough to produce ignition. A low flash point indicates that the fuel is of poorer quality or unreliable in cold conditions. The normal value for the flash point of diesel fuel is usually around 52-96°C (126-205°F). A critical value is below 52°C (126°F), which can lead to a risk of explosion when heated.


The viscosity of diesel fuel determines its ability to flow and mix with air in the engine. A low viscosity allows the fuel to atomize more easily, allowing for better mixing with air and complete combustion. A high viscosity can lead to fuel delivery problems, especially in cold conditions, and contribute to white smoke. Diesel viscosity is measured in millimeters per second (cSt). The normal viscosity range for diesel fuel is usually 2.0-4.5 cSt at 40°C. The critical value is over 4.5 cSt, which can lead to problems with fuel supply in the engine.

Sulfur content

The sulfur content of diesel fuel affects its environmental friendliness and engine durability. With a low rate, the engine wears out more slowly and fewer harmful pollutants are released into the air. Conversely, a high content can lead to contamination of parts and a greater environmental footprint. The sulfur content of diesel fuel is measured in mass units - percent or parts per million (ppm). The normal sulfur content for diesel fuel is usually less than 15 ppm. The critical value is more than 15 ppm, and it is advisable to refuse such fuel. This indicates its low quality.

Water content

The water content of diesel fuel can cause problems with storage and engine efficiency. Water can cause corrosion and deposit formation in fuel lines and injection systems, which can lead to erratic engine operation. The water content of diesel fuel is measured as a percentage. The normal water content for diesel fuel is usually less than 0.05%. A critical value is more than 0.05%, which can lead to corrosion and deposit formation in the fuel system. 

Calorific value

The calorific value of diesel fuel indicates its energy output and efficiency. A high calorific value means more energy can be released when the fuel is burned, which improves engine performance. The normal calorific value for diesel fuel is usually in the range of 42-46 megajoules per kilogram or 36.9-42 megajoules per liter. A low calorific value may indicate poor fuel quality or contamination, which negatively affects engine efficiency. This is an extremely important criterion, so if the values are out of the normal range, we recommend that you refuse to use the fuel. 


The volatility of diesel fuel indicates its ability to vaporize and form vapors under certain conditions. A high volatility contributes to easy engine starting and improved engine performance in cold conditions. The normal range of volatility for diesel fuel is usually 149-371°C. Volatility values outside this range can lead to engine starting problems, especially in cold weather, as well as unstable fuel performance.


The color of diesel fuel is an important indicator of its quality and purity. Pure diesel fuel is colorless or light yellow. The presence of an unnatural color, such as dark green or black, may indicate contamination or deterioration of the fuel quality. Normal diesel fuel has a clear and consistent color that meets quality standards.

Idol Energy uses only high-quality diesel, gasoline and NPG. We are very strict about controlling, complying with standards and improving the quality of refined products. The first thing that was created at our own refineries was the latest laboratories equipped with modern equipment. The quality of petroleum products is assessed at every stage - from receiving raw materials to shipping finished diesel to the customer. Every year we invest heavily in technologies to improve the accuracy of control and product quality. Choosing Idol Energy, you choose Quality Diesel. 

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