How Often Should I Change Transmission Fluid?

It depends on your vehicle and driving habits.

That’s a cop-out. But, it’s true.

Automatic-transmission-fluid-change recommendations vary from one original equipment manufacturer (OEM) to another. Plus, if your driving habits are like most motorists and fall under the “severe” designation (towing, hauling, daily short trips less than 10 miles, etc.), many OEMs recommend changing transmission fluid more frequently.

Check your owner’s manual

Start by looking in your vehicle owner’s manual. It’ll provide maintenance recommendations, typically in a table in the back.

The 2017 Ford F-150, for example, requires automatic transmission fluid changes every 150,000 miles in normal service, 30,000 miles if you tow and haul. My wife’s Honda CR-V calls for transmission fluid changes every 90,000 miles in normal service, 30,000 miles in severe service. Some transmissions are considered “fill-for-life”.

These differences illustrate the importance of digging your owner’s manual out from under the napkins and broken sunglasses in your glove box and checking for yourself.

Go by the book, but when you don’t…

But, really, how many of us dutifully follow the recommendations in our owner’s manuals down to the mile? True, some of us look forward to working in the garage on the weekend. But most motorists don’t have the time, which means fluid-change recommendations morph into loose suggestions, something you fit into your schedule “sometime before winter, maybe.”

But soon you’re loading down the Family Truckster for the first summer trip to the beach, yet the tranny fluid still hasn’t been changed.

Not good, especially if you tow or haul. Not good, especially if you tow or haul.

Heat kills transmissions

Over time, transmission fluid oxidizes (chemically breaks down). High heat generated from towing and hauling speeds the process. Fluid that has broken down can cause sludge and varnish to form, which clogs narrow oil passages and contributes to clutch glazing. Soon, your vehicle can begin to shift hard, jerk or hesitate.

In these cases, wouldn’t it be great to use a transmission fluid formulated with reserve protection against heat in case life gets in the way of recommended maintenance?

AMSOIL Signature Series Synthetic Automatic Transmission Fluid’s built-in reserve protection means it lasts for twice the OEM’s severe-service drain interval. That means you can rest assured your transmission is protected, even if service is delayed.

In fact, after 180,000 miles in taxi cabs driven in the searing Las Vegas heat, Signature Series retained 83 percent of its oxidation inhibitors, proving its long-lasting resistance to thermal breakdown. Plus, the used fluid with 180,000 severe-service miles on it still met the Chrysler ATF+4 standard’s new fluid requirement for resistance to thermal breakdown.

AMSOIL also offers OE Synthetic Transmission Fluid, which provides excellent protection for OEM-recommended service intervals for those of us who don’t require the reserve protection of Signature Series.

Fill for life?

I should mention “fill-for-life” transmissions, which are becoming more common as OEMs continue to look for ways to simplify (dumb-down) vehicle maintenance. Most don’t even have a dipstick for checking fluid. On those that do, they can be located in hard-to-access areas. In these cases, check a service manual for dipstick location and instructions for checking the fluid. Although the transmission is designed to be “filled for life,” that typically means fill for the life of the warranty. It’s just as important to service these units and replace the fluid once in a while to ensure the transmission lasts as designed and gives you years of solid performance beyond the OEM’s warranty period.