Is a transmission flush necessary?

Short answer: GM doesn't recommend transmission flush machines, and Honda says a transmission flush isn't necessary except in very rare cases. Changing the fluid when your owner's manual says it's due is a different job. Your owner's manual is the place to check.

We're not mechanics, so the facts below come straight from carmakers and the Federal Trade Commission. The sources are linked at the bottom.

What a transmission flush is

It's a service where a shop hooks a machine up to your transmission to push the old fluid out with new. A fluid change, the way carmakers describe it, means draining the old fluid and refilling it at the times your owner's manual lists.

What carmakers say

GM, in a 2024 service bulletin covering its 2025 and older cars and trucks with gas engines: "The use of external transmission fluid exchange or flush machines is not recommended for the automatic or manual transmission." GM adds that using those machines "may affect the operation or durability of the transmission," and that the fluid should only be replaced by draining and refilling it.

Honda, in a 2019 position statement for its Acura cars: "Transmission flushing: This procedure is not necessary, except in very rare instances (for example, to remove improper fluids). Transmission fluid replacement (as opposed to flushing) is recommended only at the mileage intervals specified in the Acura owner's manual."

Toyota, in its 2025 Corolla Cross maintenance guide: the transmission fluid gets checked at set mileages, and replaced only if you tow, use a car-top carrier, carry heavy loads, or do a lot of idling and slow driving, like delivery work.

What the FTC says

The Federal Trade Commission tells drivers to "follow the manufacturer's maintenance schedule in your owner's manual for your type of driving." It also notes that some shops create their own maintenance schedules, "which call for more frequent servicing than the manufacturer's recommendations."

What to say at the counter

"Is a transmission fluid change due on my car's maintenance schedule? If not, why do you recommend a flush?"

If it is due, ask whether they'll drain and refill it, the way GM describes, or use a flush machine.

The FTC suggests asking a shop to explain "why it recommends service beyond the recommended schedule."

For other cars

Check the maintenance schedule in your owner's manual. If a transmission fluid change isn't due yet, ask the question above.

Got an estimate with a transmission flush on it? Backseat Mechanic members text us a photo of it and find out what to fix today, what can wait, what to skip and whether the price is fair. See how it works

This is general information, not a diagnosis of your car. If your car shifts hard, hesitates or leaks fluid, get it checked. Your owner's manual is the final word.

Sources

Backseat Mechanic

Skip the manual. Text us your estimate.

We'll look up your car's maintenance schedule and check your estimate against it. You'll hear back in minutes with what to fix today, what can wait, what to skip and whether the price is fair.

Join Backseat Mechanic

$12 a month. Cancel anytime.

See how it works