What oil do I use for manual transmission?
Use the fluid your vehicle manufacturer specifies. In most manuals, this means a manual transmission fluid (MTF) or a gear oil in a defined viscosity (commonly 75W-90 or 80W-90), with either GL-4 or GL-5 specifications depending on the model. Always verify with the owner's manual or dealer before purchasing.
How to determine the correct fluid for your car
To ensure you pick the right oil, follow these steps and keep it simple at the start with the official guidance from your car’s maker.
- Consult the owner’s manual or the manufacturer’s website for the exact spec (category, viscosity, and whether it calls for GL-4, GL-5, or an MTF fluid).
- Check the transmission fill/drain port for the specified grade or part number; some cars list it on the dipstick or near the fill plug.
- If you can’t locate the manual, contact a dealer or a trusted mechanic who can confirm the exact fluid for your model and year.
- Do not substitute engine oil or ATF unless the manual explicitly allows it.
Using the correct fluid helps ensure smooth shifting, proper synchronizer function, and longevity of gears. Using the wrong type or an incorrect viscosity can cause gear crunching, slipping, or accelerated wear.
Common oil types used in manual transmissions
The following guide covers the main fluid types you might encounter. The exact specification for your car is found in the owner’s manual or service bulletin.
- MTF — Manual Transmission Fluid. A dedicated fluid designed for synchronizers and gears in many manuals; common viscosities include 75W-80, 75W-90, or similar. Some cars require MTF with a GL-4 rating, while others may accept GL-5 or a blended spec.
- Gear oil GL-4 — Traditional manual gearbox oil used in many older or certain European/Japanese transmissions with brass synchronizers.
- Gear oil GL-5 — A high-performance EP oil used in many modern manuals; many vehicles specify GL-5, but always confirm the exact spec for your model to avoid compatibility issues with synchronizers.
- ATF — Automatic transmission fluid. Generally not used in manuals unless the manufacturer explicitly requires it; using ATF in a non-specified manual can lead to shifting issues or wear.
- Synthetic vs conventional — Synthetic gear oils can provide better temperature performance and longevity, and many MTFs are synthetic blends or fully synthetic; follow the manufacturer’s recommendation about using synthetic vs conventional.
Not every vehicle follows the same rule. Always confirm with the manual or dealer for the exact grade, specification, and whether MTF or a gear oil is required.
Practical steps for changing or topping up manual transmission fluid
When performing a fluid change or top-up, follow proper procedure to ensure correct fill level and clean oil. The steps below reflect common practice, but always refer to your model’s service manual.
- Warm the vehicle lightly and raise it safely, then place it on jack stands or a ramp as needed.
- Place a drain pan under the fill/drain plug and remove the drain plug to drain old fluid completely.
- Replace the drain plug with a new gasket if required and torque to spec.
- Install the fill plug and add the correct quantity of fluid until it reaches the designated level (as indicated by the fill hole or level mark).
- Dispose of used oil responsibly and recycle at an approved facility.
Proper draining and filling help ensure optimal lubrication and shift performance. Never mix fluids unless the manual explicitly allows it, and avoid overfilling, which can cause foaming and leakage.
Summary
The key takeaway is to follow the manufacturer’s specification for manual transmission oil. Most manuals require either a dedicated MTF or a GL-4/GL-5 gear oil at a specific viscosity (commonly around 75W-90), with ATF only used if the maker explicitly allows it. Always consult the owner's manual or your dealer/mechanic to confirm the exact fluid for your vehicle and climate, and perform regular maintenance using clean, properly measured quantities.
