What is the difference between gear grease and oil?

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%.

1. 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.

2. Thickener

Thickener is an important component of grease. Thickener is dispersed in base oil and forms the structural skeleton of grease, so that the base oil is 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 composite soap (such as composite calcium-based grease). 90% of greases are made with soap-based thickeners.

3. Additives and fillers

One type of additive is required for 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.

You will find that lubrication is basically similar to grease, except that grease has an additional thickener.

So what is the difference between grease and lubricant applications and how to choose?

The main reasons for choosing grease are:

1. Cost-effectiveness

2. 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 complex sealing configuration

The main applications for grease selection exceptions:

The working conditions require that the grease relubrication interval is too short to be accepted

Lubricating oil must be used for other reasons (for example, in gearboxes)

Oil lubrication needs to be considered when heat dissipation through circulating oil is required

When cleaning or removing used grease becomes cumbersome or expensive.