Are grease and oil the same? What is the difference?
author: Ann
2024-07-29
Lubricating oil generally consists of two parts: base oil and additives. Base oil is the main component of lubricating oil and determines the basic properties of lubricating oil. Additives can make up for and improve the deficiencies in the performance of base oil and give it some new properties. They are an important part of lubricating oil.
Grease is mainly composed of three parts: thickener, base oil and additives. The content of thickener in general grease is about 10%-20%, the content of base oil is about 75%-90%, and the content of additives and fillers is less than 5%.
Grease is mainly composed of three parts: thickener, base oil and additives. The content of thickener in general grease is about 10%-20%, the content of base oil is about 75%-90%, and the content of additives and fillers is less than 5%.
About base oil
Base oil is the dispersion medium in the grease dispersion system, which has a great influence on the performance of grease. Generally, greases use medium-viscosity and high-viscosity petroleum lubricants as base oils. Some greases use synthetic lubricants as base oils to meet the needs of mechanical lubrication and sealing under harsh conditions, such as ester oils, silicone oils, poly-α-olefin oils, etc.
About thickeners
Thickeners are important components of greases. Thickeners are dispersed in base oils and form the structural skeleton of greases, so that the base oils are adsorbed and fixed in the structural skeleton. The water resistance and heat resistance of grease are mainly determined by the thickener. There are two major categories of thickeners used to prepare grease. Soap-based thickeners (i.e. fatty acid metal salts) and non-soap-based thickeners (hydrocarbons, inorganic and organic).
Soap-based thickeners are divided into three types: single soap (such as calcium-based grease), mixed soap (such as calcium-sodium-based grease), and complex soap (such as complex calcium-based grease). 90% of greases are made with soap-based thickeners.
About additives and fillers
One type of additive is carried by grease, called peptizer, which makes the combination of oil and soap more stable, such as glycerol and water. Once calcium-based grease loses water, its structure is completely destroyed and cannot form grease. For example, glycerol can adjust the consistency of grease in sodium-based grease.
Another type of additive is the same as that in lubricating oil, such as antioxidants, anti-wear and rust inhibitors, but the amount used is generally more than that in lubricating oil. Such as phosphate esters, ZDDP, Elco extreme pressure anti-wear agents, compounding agents, dropping point enhancers, etc. Sometimes, in order to improve the ability of grease to resist loss and enhance lubrication, some graphite, molybdenum disulfide and carbon black are often added as fillers.
To sum up, you will find that the composition of lubricating oil and grease is basically similar, except that grease has an additional thickener.
So what is the difference between grease and lubricant in application, and how to choose?
Lubricating oil is more complicated because of different classifications and different places of use. Relatively speaking, the choice of grease is relatively simple, mainly for two reasons: first, saving money and pursuing cost-effectiveness; second, simple, grease is easy to retain on the gear surface or in the gearbox, so compared with oil lubrication, it does not require a very complicated sealing configuration.
When should you use lubricating oil instead of grease?
Working conditions: When the lubrication interval of grease is too short to be accepted, lubricating oil is needed;
When lubricating oil must be used for other reasons, such as in a gearbox;
When heat dissipation through circulating oil is required, lubricating oil should be considered;
When cleaning or removing used grease becomes cumbersome or expensive, lubricating oil can be directly considered.
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