Transmission fluid change: when you need one and why it matters

What the fluid does

• Lubricates the gears, bearings and clutches inside the transmission.
• Carries heat away. Heat is the main thing that wears transmissions out.
• In an automatic, it is also the hydraulic fluid that makes the transmission shift. Worn fluid can mean slower, harsher shifts.

How often to change it

Check the maintenance schedule in your owner’s manual. Some give a mileage interval, some only call for a change under severe service, and some describe the fluid as "lifetime". Severe service usually includes frequent stop-and-go driving, lots of idling, short trips, towing, hot weather and commercial use such as taxi and rideshare. In New York City most cars meet at least one of those, so the severe schedule is often the one to follow.

Signs the fluid needs attention

• The fluid is dark brown or smells burnt instead of being red or pink. Some cars have no dipstick, so it has to be checked on a lift.
• Shifts have become slower, harsher or less smooth.
• Red or brownish drops under the middle of the car. That is a leak, and it should be fixed first.
• A transmission temperature or warning light.

The right fluid matters

There are many types of transmission fluid: different automatic fluids, CVT fluid, dual-clutch fluid and gear oil for manuals. They are not interchangeable, and the wrong one can cause shifting problems or damage. A "universal" fluid is not a substitute for what your manufacturer specifies.

Drain and fill or flush

A drain and fill replaces part of the fluid, because some stays inside the torque converter and lines. A flush uses a machine to exchange more of it. Which one is right depends on the transmission and on what the manufacturer specifies. If a transmission is already slipping or shifting badly, new fluid alone may not fix it, so get it diagnosed first.

How we handle it here

• We check the level and condition of the fluid and look for leaks before recommending anything.
• We do transmission fluid service in our shop with the fluid type your manufacturer specifies, following its procedure.
• We give you the price before any work starts, and nothing is done without your approval.
• We are open 24 hours a day, 7 days a week, and we speak English and Spanish.