Gearbox Oil, ATF, DSG and CVT Fluid Explained

Gearboxes are far less forgiving of the wrong fluid than engines. A manual gearbox, an automatic, a dual-clutch DSG and a CVT each need a different type of fluid, and within each type the car maker's specification matters. This guide explains the main types and how to choose.

Manual gearbox oil

Manual gearboxes use gear oil, rated with its own viscosity grades such as 75W, 75W-80, 75W-90 and 80W-90, and an API rating:

• API GL-4 is for most manual gearboxes, including those with brass synchronisers.
• API GL-5 has more extreme-pressure additives for hypoid gears in axles and differentials. In some older gearboxes designed for GL-4, those additives can attack brass synchronisers.

Use GL-4 where your handbook asks for it. Some oils are rated GL-4 and GL-5 together, which makes them safe for both uses. Shop manual gearbox oil, 75W-90 and 75W-80.

Differential and axle oil

Rear axles and differentials normally need GL-5 oil, often 75W-90, 80W-90 or 75W-140. A limited-slip differential (LSD) needs an oil with limited-slip additives, labelled LS. Shop differential and axle oil.

Automatic transmission fluid (ATF)

Conventional automatic gearboxes use ATF. Car makers set their own ATF specifications, for example Dexron, Ford Mercon, Mercedes-Benz MB 236.14 and 236.15, ZF LifeguardFluid, Toyota WS and Aisin JWS 3309. Multi-vehicle ATFs are formulated to cover a list of these specifications, and the list is printed on the product. Always check that your gearbox's specification is on it. Shop automatic transmission fluid.

DSG and dual-clutch fluid

Dual-clutch gearboxes, such as VW Group DSG, come in two main designs. Wet-clutch units, such as many 6-speed DSG gearboxes, need a dedicated DSG fluid. Dry-clutch units, such as the 7-speed DQ200, use a different gear oil. Check which gearbox you have before you order. Shop DSG and DCT fluid.

CVT fluid

Continuously variable transmissions (CVT), used by Nissan, Honda, Toyota and others, need a CVT-specific fluid, such as Nissan NS-2 or NS-3, or Honda HCF-2. Never use ordinary ATF in a CVT unless the maker specifically allows it. Shop CVT fluid.

Power steering and hydraulic fluid

Hydraulic power steering uses either a dedicated fluid, such as Pentosin CHF 11S, or a specified ATF. Many newer cars have electric steering and need no fluid at all. Shop power steering and hydraulic fluid.

How often should gearbox fluid be changed?

Follow the service schedule for your car. Many manufacturers describe automatic gearbox fluid as a lifetime fill, but gearbox specialists often recommend a change during the vehicle's life, especially for cars that tow or cover high mileage. DSG gearboxes often have a set fluid-change interval in the service schedule.

Frequently asked questions

Can I use engine oil in a manual gearbox?

Only if your handbook says so. A few gearboxes are designed for engine oil, but most need a gear oil that meets a specific API rating and viscosity.

Is ATF the same as DSG fluid?

No. DSG and dual-clutch fluids are made for the wet clutches in those gearboxes. Use the fluid your gearbox specifies.

Can I mix different ATFs?

It is best not to. If you need to top up, use a fluid that meets the same specification as the one in the gearbox.