Gear / Transmission oil

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A gearbox/transmission consists of moving metal components that transfer the power from an engine to the drive shaft of an automobile. Metal components moving against each other results in friction, for this reason a lubricating agent called ‘Gear oil’ or ‘Transmission oil’ is used to reduce friction inside a gearbox. 

There are different grades of gear oil on the market. Car manufacturers recommend a specific grade of gear oil for a vehicle depending on the design of the gearbox along with the periodical interval for gear oil replacement. A vehicle’s owner’s manual will specify the grade of gear oil to be used just like it specifies the grade of engine oil a vehicle requires.

There are different types of gear oil for automatic and manual gearboxes as they function differently. It would be worth mentioning that some modern automatic gearboxes are emerging which manufacturers recommend do not need a gear oil change for as long as 2,40,000 kms owing to a low-friction design. An example of this is the new Ford Fiesta automatic that has a double clutch gearbox. 

Gear oil however is different from engine oil in terms of additives used. Engine oil is pumped around the engine to create a lubricating film around bearings. While gear oil consists of extreme pressure additives that allow it to lubricate the surface of the gears without air bubbles forming under high pressure between contacting rotating gears. Also, gear oil has to be able to stick onto rotating gears as there is no pump that circulates gear oil, instead channels are designed inside a gearbox to direct oil flow. 

Synthetic gear oil is also available in the market and can significantly improve the duration between oil changes. Synthetic gear oil can also perform better than conventional mineral based gear oil under extremely low or high temperatures along with better lubricating properties. Disadvantages of synthetic gear oils lie in their high cost and material compatibility problems such as corrosion of rubber seals. 

Some common gear/transmission oil brands are Castrol, AMSOIL, Valvoline, Pennzoil, Shell, etc. Prices for gear oil starts from Rs. 300 per litre onwards to Rs. 850 per litre onwards for synthetic gear oil.