Diesel is a light petroleum product mainly composed of carbon, hydrogen, and some oxygen. It is refined from crude oil and can also be obtained through shale oil processing and coal liquefaction. The color of diesel is not a fixed standard as it is influenced by various factors, including the quality of crude oil, refining processes, and degree of purification. Therefore, diesel produced by different refineries may vary significantly in color.
According to national standards, the color of light diesel should not exceed 3.5. Color is used as an indicator of diesel color, and different colors may indicate different qualities and performances. For example, darker diesel may contain more impurities or additives, which can affect the quality and performance of diesel.
Generally, diesel should be yellow to golden yellow, but this also depends on the aforementioned factors. Sometimes, diesel may undergo oxidation upon exposure to air, producing red substances, resulting in a reddish-brown color.
When choosing diesel, color is not the only important factor; more important is whether the diesel is pure and free from impurities. Clear diesel is usually better as it indicates thorough refining, reducing the content of harmful substances.
In summary, the color of diesel can vary from yellow to golden yellow depending on the source of crude oil, refining methods, and degree of purification. When purchasing diesel, in addition to color, other quality indicators such as sulfur content, density, water content, and mechanical impurities should also be considered to ensure the quality and suitability of diesel.