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Gearbox oil is essential to unlocking the range of performance your vehicle needs. Discover Castrol's gear oils from standard mineral to synthetic oils.

Gear Oils

Gear oils

Gear oils are vital to protecting all transmission systems whether you are looking for a smooth drive in your car or smooth performance from your machinery. Whether you are looking for a manual gearbox oil or gear lubrication for your automatic car or industrial gearbox oil for working machinery, our comprehensive range of gearbox fluids delivers the performance you need.


Types of gear oil

Castrol have gearbox oil types and transmission fluids for every need from standard mineral oils to high performance synthetic gearbox oils. Find the right gear oil  for your vehicle.


Gear oil FAQs

Q: Can I put a transmission fluid into a manual gearbox?

A: Sometimes! Some manual gearboxes do take transmission fluids. Always check your Owner’s Manual to see what is recommended for your system.

Q: Can I put a gear oil into an automatic transmission?

A: No. Gear oil is too viscous to be put into an automatic transmission and will clog up its components

Q: Is there a hard and fast rule for when to change my gear oil?

A: No. This will depend on your application and usage rates. 

Q: Are there any tell-tale signs that my gear oil might need changing?

A: Yes. If you feel that your gearbox is grinding or slipping, it’s almost certainly time to change your oil.


What is gear oil?

Gear oil is a lubricant designed to protect transmissions, transfer cases, and differentials in all applications of moving machinery – cars, trucks, the aerospace industry, metal cutting, mining and wind turbines. Most gear oils have a high viscosity and contain high-pressure additives (EP) and anti-wear additives. 


When should i change gear oil?

Gearboxes and transmission systems have to contend with heat, wear and friction and gear oils are used to combat and manage these effects. If your fluids are leaking or in need of a change you will experience grinding or slipping of your gears whether you are driving a car or working with machinery.

It is important to check the condition of your gearbox fluids regularly. If the chemicals and additives inside the fluid start to degrade, it’s time for a change. 


Transmission oil vs gear oil

As a rule of thumb, gear oil is used in manual gear boxes and transmission fluid in automatic transmissions . To answer this question at a deeper level, we need to look at the key differences between gearboxes and transmissions.


Gearboxes and transmissions do the same job. They both facilitate changes through the gears to control the speed, force and direction of travel but they do this in different ways. 


Manual gearboxes generate a lot of heat caused by a lot of friction. This places an emphasis on helping gears through transitions as smoothly as possible. This necessitates a thicker, more viscous oil able to withstand high temperatures and able to function under extreme pressure.


Automatic transmissions switch gears automatically depending on the demands of the engine. They contain more moving parts than a manual gearbox and need to transfer power from the oil pump to the clutches which control the movement of the gears.


This necessitates a much less viscous and thinner gearbox fluid. Transmission fluids contain detergents and act as coolants. They have a lower boiling point than gear oil and contain further additives in order to improve their life expectancy.

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