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.