30/05/2022 by OilStoreAdministrator
High temperatures can result in lubricants like oil and other fluids evaporating. Volatile components within the lubricant’s base oil start to become gaseous, causing the solution to thicken. As a result, the oil’s viscosity alters, along with the level of lubrication the oil can provide. In this article, we’ll explore evaporation loss in lubricating oils in depth.
The impact of evaporation loss
Evaporation loss is an exceptionally important quality, particularly for engine oils. High levels of evaporation loss will inevitably lead to much higher oil consumption, making the intervals between oil changes far shorter. If an oil’s viscosity changes and becomes thicker, it will no longer be able to transfer the correct lubrication properties when required to ease friction. As a result, there is a rise in energy demand, along with an associated increase in fuel consumption. This thickening effect also promotes the formation of unwanted sludge in engine compartments. For these reasons, engine oils that have low evaporation loss are often desirable.
Evaporation loss also has an important part to play in industrial lubricants, leading it be a key quality feature for any chain lubricants used in processes where high operating temperatures are involved.
How do you measure evaporation loss?
Evaporation loss in a lubricant is determined in accordance with DIN 51581 using the NOACK evaporation test. Named after Kurt Noack, the NOACK value is represented in percent. This is utilised to determine the precise percentage weight loss of an oil in a well-established and standardised testing procedure. When a NOACK test is undertaken, an oil sample is heated up to 250°C and then exposed to a continuous airflow. After a period of one hour, the mass of the oil sample is measured to determine how much of the mass has evaporated.
The NOACK test is based on engine oil’s operating conditions. It is designed to replicate the high temperatures oils must cope with at an engine’s piston ring while dealing with blowby gases.
What is the normal evaporation loss of engine oil?
Many auto manufacturers, as well as the ACEA (the European Automobile Manufacturers Association), set limit values on the evaporation loss of oils designed for engines. These limits are regulated within individual specifications. Most modern engine oils will have approximate evaporation losses of between 5 to 13 per cent. However, only NOACK values of engine oils that are part of the same SAE (Society of Automotive Engineers) class can be compared.
In sum, to ensure a lubricant is dependable and offers optimum performance, low evaporation loss is always a sought-after quality when selecting a product.
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