The most important reasons why synthetic gear oil is best.

 When purchasing gear lubricants do you know why synthetic gear oil is best? Have you ever felt like a kid in a candy store when trying to select synthetic gear oil from a glitzy pamphlet? How many times would you have paid someone to explain why synthetic gear oil is best?

Why synthetic gear oil is best in tough conditions.

Like synthetic gear lubricants in any application, synthetic gear oil is usually used whenever mineral gear oil has reached the performance limit and can no longer meet the application requirements; for example, at very low or high temperatures, extremely high loads, extraordinary ambient conditions, or if they fail to meet special requirements such as flammability.

Even though additives can improve many properties of mineral oils, it is not possible to modify all their properties, which is why synthetic gear oil is best in extreme conditions. This applies especially to physical properties such as:

• evaporation losses 
• thermal resistance 
• flash point 
• low temperature properties (fluidity, pour point) 

These are reasons why synthetic gear oil is best. However, it does not necessarily out-perform mineral oil in all respects and may even result in some drawbacks despite the advantages.

Reasons why synthetic gear oil is best (depending on the base oil):

• lower evaporation losses 
• improved lubricity (in some cases) 
• improved thermal and oxidation resistance
• improved viscosity-temperature behavior, high viscosity index (in most cases) 
• improved low temperature properties 
• reduced flammability (in some cases) 
• lower tendency to form residues 
• improved resistance to ambient media 

Although there are several reasons why synthetic gear oil is best, possible disadvantages include:

• limited miscibility with mineral oils 
• higher price 
• reactions in the presence of water (hydrolysis, corrosion) 
• material compatibility problems (paints, elastomers, certain metals) 

Application-related advantages are often why synthetic gear oil is best, especially under critical operating conditions. The most common synthetic types used include synthetic hydrocarbon oils (SHC), polyglycols (PAG) and ester oils (E).

So, what are the different types of synthetic gear oil available.

Lubricating Oils Based On Synthetic Hydrocarbon Oils
Synthetic hydrocarbons are similar to mineral hydrocarbons in their chemical structure. They have nearly identical properties relating to their compatibility with sealing materials, disposal, reprocessing and miscibility with mineral oils. The reason why this synthetic gear oil is best is the excellent low temperature behavior.

Lubricating Oils Based On Polyglycols
These lubricants ensure especially low friction coefficients, which makes them suitable for gears with a high sliding percentage (worm and hypoid gears). With the appropriate additives, they provide excellent antiwear protection in steel/bronze worm gears, and have a good extreme pressure performance. In gear systems, higher polarity polyglycols allow greater interaction on the metal gear surface. This gives polyglycols mild extreme pressure performance even without additives.

Polyglycol oils may have a negative impact on sealing materials and may dissolve some paints. At operating temperatures above 100°), only seals made of fluorinated rubber or PTFE are resistant. Before using PAG oils in production applications, it is advisable to test compatibility with paints, seals and sight glass materials.

Miscibility with mineral oils is limited; mixtures should therefore be avoided. Polyglycols are neutral toward ferrous metals and almost all nonferrous metals. If the application has a loaded contact with one component consisting of aluminum or aluminum alloys (rolling bearing cages containing aluminum), there may be increased wear under dynamic load (sliding movement and high load). In such cases, compatibility tests should be conducted before switching to make sure this type of synthetic gear oil is best for the application. If a worm gear is made of an aluminum bronze alloy, polyglycols should not be used because the reaction in the load zone could result in increased wear.

Lubricating Oils Based On Ester Oils
Ester oils are the result of a reaction of acids and alcohols with water splitting off. There are many types of esters, all of them having an impact on the chemical and physical properties of synthetic gear oil. In the past, these lubricating oils were used in aviation technology for the lubrication of aircraft engines and gas turbines as well as gear systems in pumps, starters, etc.

Ester oils have a high thermal resistance and excellent low temperature behavior. In industrial applications, rapidly biodegradable ester oils will gain importance because it seems possible to achieve the same efficiency as with polyglycol oils by selecting an appropriate ester base oil.

Certain ester oils may exhibit low hydrolytic stability. Hydrolysis is the cleavage of the ester into an alcohol and an acid in the presence of water. Ester lubes need to be hydrolytically stable because they are often exposed to humidity in use. In practice, hydrolysis may be a less serious problem than commonly reported. The hydrolytic stability of an ester depends on:

• how the ester was processed 
• the type of ester used 
• the type of additives used 
• the application 

Now that we know why synthetic gear oil is best, you can get the best advice and synthetic lubricants from the professionals at Habot Oil.