Mechanic says yes, you should change the transmission fluid even if it’s a ‘seal for life transmission’ on newer cars

@motorcarnut/TikTok standret/Adobe Stock deagreez/Adobe Stock (Licensed)

‘People don’t even check under the hood’: Mechanic says yes, you should change the transmission fluid even if it’s a ‘seal for life transmission’ on newer cars

‘It’s not a miracle fluid.’


Parks Kugle


If you ever have a tough time shifting gears, notice gears taking too long to engage, or find fluid pooled underneath your parked car, it may be time to change the transmission fluid.

What is transmission fluid?

Similar to motor oil, transmission fluid is a vital component in every vehicle. According to Kelley Blue Book, transmission fluid is composed of mineral oil or a synthetic blend with anti-oxidation and anti-corrosion additives. It helps engines function smoothly. Specifically, the fluid allows automatic transmissions to transition smoothly between gears while driving. Without it, the system that powers a vehicle from the engine to the wheels will break down.

Kelley Blue Book also states that guidelines on when to change transmission fluid vary by vehicle make and model and can range from needing the dealership service center to check the fluid and “replace as necessary” to a set interval like every 60,000 miles.

Though this fluid is so important, many people don’t even realize that it needs to be changed on a regular basis. In an effort to dispel this illusion, TikToker Motorcarnut (@motorcarnut) posted a viral video that explained not only why people should change their transmission fluid but also summarized how the procedure for checking it works. The video has been viewed over 275,000 times as of this writing.

The first thing Motorcarnut does is point out how many new vehicles no longer have a dipstick, which puts a slight wrinkle in quickly checking the transmission fluid’s condition. However, he also points out that if you don’t have a dipstick, then you likely have a “seal for life transmission.”

“That doesn’t mean the life of the ownership,” Motorcarnut says. “You have to change that just like you would change any other type of fluid. It’s not a miracle fluid. It’s regular transmission fluid.”

@motorcarnut No transmission dipstick? #motorcarnut #cars #mechanic #mechaniclife #mechanicsoftiktok ♬ original sound – Motorcarnut

What is a “seal for life” transmission?

According to John Cadogan of AutoExpert, “sealed for life” doesn’t mean an enclosed system that will last; rather, it means that there is no dipstick. He also believes that the term is intentionally misleading and is “an extremely cynical way for a carmaker to engineer-in epic, deal-breaking major failures.”

On top of that, Cadogan says dipstick-less transmissions may require a “scan tool” and “convoluted fluid replacement protocol,” making it harder for car owners to maintain their vehicles themselves.

Motorcarnut says the procedure for changing “sealed for life” transmission fluid usually involves “getting the car up to operating temperature and using maybe a temperature probe [or] infrared thermometer to get it done.”

Still, he says it’s possible for drivers to do it themselves and says he has videos on his channel explaining how. In one video on his YouTube channel, he shows viewers how to change the fluid in a Kia with a sealed transmission. For cars of other makes, he says, “All the manufacturers, you know, they have little similarities. You just look in the particular shop manual how to do it.”

One newer car owner shared their own method in the TikTok comments section. “My Lexus doesn’t have a dipstick but I change it every 30,000 miles,” they wrote. “I use an ODB scanner to measure transmission temperature to get the refill just right.”

Others shared their frustrations with newer car designs.

“They only intended for the transmission to last about 100,000 miles,” a viewer said.

“Pisses me off that I don’t have an oil dipstick but I do for the transmission,” another added.

Some viewers disagreed with Motorcarnut, arguing that transmission fluid never needs to be changed.

“Don’t ever change transmission fluid,” a viewer commented. “It will destroy your transmission. You need to keep the same fluid minerals in for life.”

In response to such comments, Motorcarnut suggested that saying, “Don’t ever change the transmission fluid,” was akin to saying don’t “take a shower” or “change your underwear.”

The Daily Dot reached out to Motorcarnut via TikTok comment and Kia via email for more information.

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