Apart from their appearance, what are the differences between grease and oil?
author: Ann
2025-03-10
Adhesion
When the friction part is in a static state, the grease can maintain its original shape and will not automatically flow due to gravity, nor will it slide on the vertical surface or drip out from the gap. This feature is very suitable for friction parts that are stopped and started or not often used, for parts that are very difficult to replenish grease materials (such as the lubrication parts of overhead crane aerial operations), and for open or poorly sealed parts.
When the friction part is in motion, the grease will not be thrown out by the centrifugal force like lubricating oil, nor will it splash out from poorly sealed parts. Some dripping or splashing oil can be almost completely avoided, which can ensure that the environment is not polluted or less polluted, and can also prevent contamination of products. This is especially important for industries such as papermaking, weaving, and food.
Using temperature range
The operating temperature range of grease is wider than that of lubricating oil. For example, general lithium-based grease can be used in the temperature range of -20~120℃, and general calcium-based or sodium-based grease can also be used at -20~60℃ or -20~120℃. However, the temperature range of a certain brand of lubricant is much narrower.
Pressure resistance
Grease has a much greater adsorption capacity on the metal surface than lubricant, and can form a relatively strong oil film and withstand a relatively high workload. This is because the grease contains a large amount of polar substances. In addition, when it is used as a base grease, after adding polar additives, the sensitivity is also better than lubricant.
Service life
When the grease is used for a long time without replacement, it can still ensure the lubrication effect, because only a small part of the grease close to the friction surface really plays a lubricating role, and it relies on the traction of soap fibers for circulation lubrication, so it can be seen that the service life is quite long;
Lubricant oil needs to be added frequently, or circulated, otherwise it cannot ensure the normal lubrication of the machine. In terms of quantity, the consumption of lubricant oil is 15 to 20 times more than that of grease, so there are many more parts lubricated by grease than lubricant oil. For example, about 2/3 of the lubricating parts of automobiles are lubricated with grease. On the other hand, due to infrequent refueling, the maintenance period is long, the consumption is reduced, and the maintenance cost is also low.
Lubrication equipment structure
The equipment structure using grease lubrication is relatively simple, which can simplify the design and reduce investment. In addition, the lubrication system occupies a relatively small area, and the setting of lubrication points is very flexible. When it is put into operation, it can also save maintenance and management costs. The internal space of some precision instruments, meters and electronic equipment is extremely small and does not allow a dedicated lubrication system. They need a long life or even rely on grease for lifelong lubrication. Lubricating oil needs to be lubricated in a closed system, and the structure of the lubricated equipment is also relatively complex. The investment and floor space are also large. It is not suitable for semi-enclosed or non-enclosed lubrication parts.
Protective performance
Grease will not be affected by its own weight and automatically flow away from the surface of the protective part. It has retention ability, and the grease layer is generally thicker than the oil layer, so it has a strong ability to prevent water or water vapor from penetrating into the metal surface, and can isolate acids, alkalis, moisture, oxygen and water from directly corroding the working surface. Some greases will not be dissolved by chemicals, basic organic raw materials, fuels and lubricating oils. The protective ability of lubricating oils is relatively poor, and it can only play a certain protective role in a short period of time.
Sealing performance
Grease can prevent dust from entering the working surface, prevent impurities from mixing in, and wear mechanical parts. For working parts such as bearings with complex spatial structures and high precision requirements for lubricating surfaces, grease can block dust and impurities on the outer surface of the bearing and fill the main gaps to play a sealing role. For some rough machinery such as agricultural tractors, harvesters, bulldozers, etc., the entire machinery is in contact with soil and sand. Its rotating parts are lubricated with grease, which can not only play a lubricating role, but also play a sealing role to a certain extent. But lubricating oil does not have this ability.
Buffering and shock absorption
Due to the high viscosity and good oiliness of grease, grease can play a certain buffering and shock absorption role for some machinery that often requires changing the direction of movement and withstands great impact, such as crankshafts, universal joints, crushers and other lubricating parts. On some parts, such as gear transmission devices, grease can also reduce noise, but in general, lubricating oil is poor in buffering and reducing noise.
When the friction part is in a static state, the grease can maintain its original shape and will not automatically flow due to gravity, nor will it slide on the vertical surface or drip out from the gap. This feature is very suitable for friction parts that are stopped and started or not often used, for parts that are very difficult to replenish grease materials (such as the lubrication parts of overhead crane aerial operations), and for open or poorly sealed parts.
When the friction part is in motion, the grease will not be thrown out by the centrifugal force like lubricating oil, nor will it splash out from poorly sealed parts. Some dripping or splashing oil can be almost completely avoided, which can ensure that the environment is not polluted or less polluted, and can also prevent contamination of products. This is especially important for industries such as papermaking, weaving, and food.
Using temperature range
The operating temperature range of grease is wider than that of lubricating oil. For example, general lithium-based grease can be used in the temperature range of -20~120℃, and general calcium-based or sodium-based grease can also be used at -20~60℃ or -20~120℃. However, the temperature range of a certain brand of lubricant is much narrower.
Pressure resistance
Grease has a much greater adsorption capacity on the metal surface than lubricant, and can form a relatively strong oil film and withstand a relatively high workload. This is because the grease contains a large amount of polar substances. In addition, when it is used as a base grease, after adding polar additives, the sensitivity is also better than lubricant.
Service life
When the grease is used for a long time without replacement, it can still ensure the lubrication effect, because only a small part of the grease close to the friction surface really plays a lubricating role, and it relies on the traction of soap fibers for circulation lubrication, so it can be seen that the service life is quite long;
Lubricant oil needs to be added frequently, or circulated, otherwise it cannot ensure the normal lubrication of the machine. In terms of quantity, the consumption of lubricant oil is 15 to 20 times more than that of grease, so there are many more parts lubricated by grease than lubricant oil. For example, about 2/3 of the lubricating parts of automobiles are lubricated with grease. On the other hand, due to infrequent refueling, the maintenance period is long, the consumption is reduced, and the maintenance cost is also low.
Lubrication equipment structure
The equipment structure using grease lubrication is relatively simple, which can simplify the design and reduce investment. In addition, the lubrication system occupies a relatively small area, and the setting of lubrication points is very flexible. When it is put into operation, it can also save maintenance and management costs. The internal space of some precision instruments, meters and electronic equipment is extremely small and does not allow a dedicated lubrication system. They need a long life or even rely on grease for lifelong lubrication. Lubricating oil needs to be lubricated in a closed system, and the structure of the lubricated equipment is also relatively complex. The investment and floor space are also large. It is not suitable for semi-enclosed or non-enclosed lubrication parts.
Protective performance
Grease will not be affected by its own weight and automatically flow away from the surface of the protective part. It has retention ability, and the grease layer is generally thicker than the oil layer, so it has a strong ability to prevent water or water vapor from penetrating into the metal surface, and can isolate acids, alkalis, moisture, oxygen and water from directly corroding the working surface. Some greases will not be dissolved by chemicals, basic organic raw materials, fuels and lubricating oils. The protective ability of lubricating oils is relatively poor, and it can only play a certain protective role in a short period of time.
Sealing performance
Grease can prevent dust from entering the working surface, prevent impurities from mixing in, and wear mechanical parts. For working parts such as bearings with complex spatial structures and high precision requirements for lubricating surfaces, grease can block dust and impurities on the outer surface of the bearing and fill the main gaps to play a sealing role. For some rough machinery such as agricultural tractors, harvesters, bulldozers, etc., the entire machinery is in contact with soil and sand. Its rotating parts are lubricated with grease, which can not only play a lubricating role, but also play a sealing role to a certain extent. But lubricating oil does not have this ability.
Buffering and shock absorption
Due to the high viscosity and good oiliness of grease, grease can play a certain buffering and shock absorption role for some machinery that often requires changing the direction of movement and withstands great impact, such as crankshafts, universal joints, crushers and other lubricating parts. On some parts, such as gear transmission devices, grease can also reduce noise, but in general, lubricating oil is poor in buffering and reducing noise.
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