According to most automotive experts, the best way to make sure which types of maintenance your car needs is to check the owners manual.

But almost no owners manuals say anything about a transmission fluid exchange, so it must be a bogus service, right? It’s just the shop’s way of trying to sell some unnecessary work and make a few extra bucks.

It seems logical, but no: A transmission fluid exchange is a real service, and it comes with a whole slew of real benefits.

So why doesn’t it appear in the owners manual?

Transmission Service Explained

To begin with, for many cars on the road, a transmission fluid exchange service didn’t exist when the car was being built. The technology was just being introduced, and only a few shops offered the service. It’s only become a common service in the last few years.

Even fewer dealers offered transmission fluid exchange services back when those cars were being built, and there was no way the manufacturer wanted to recommend a service that you’d have to take to someone other than their dealers.

Let’s not forget that auto manufacturers introduce a new car line every year. Recommending too much regular maintenance might make their cars seem less desirable than their competitors’ cars. And if last year’s model doesn’t last forever, well, doesn’t that really work out better for them?

What the owners manual does recommend is a regular transmission service. On most cars, a principal element of that service usually includes removing the transmission pan, draining the transmission fluid, and replacing it with fresh fluid.

But there’s a downside to the basic service: It only replaces a few quarts… in most cases, no more than about a third of the fluid in the transmission.

Replacing the transmission fluid is important because automatic transmission fluid (ATF) does more than just lubricate and cool the transmission. When squeezed down between the clutch plates, the transmission fluid actually helps the clutches grab.

But, over time, transmission fluid can wear out through a process called shear. It’s what happens to the transmission fluid through extended exposure to heat and oxidation. And fluid shear can cause the transmission to slip.

Replacing the fluid eliminates shear; the fresh fluid helps the clutches grab and that can keep the transmission operating longer.

Fluid Exchange Service

But remember, the basic transmission service only replaces a small part of that worn, sheared oil. A fluid exchange service replaces a lot more: in most cases more than 90% of the existing fluid will be replaced. And that can mean your transmission will last longer and provide more years of dependable service.

So yes, a transmission fluid exchange is a real service, and it’s one that can keep your car on the road for years to come.

To learn more, or to schedule a transmission service, contact your nearby Cottman center.