Should I Change Transmission Fluid After 100k Miles?

Transmission fluid lubricates the various moving parts in your car’s transmission to boost its performance. If you have an automatic transmission, it also acts as a coolant while also helping transfer engine power to your transmission.

Just like your engine oil, over time, the transmission fluid will deteriorate. As it becomes dirty and clogged with debris, it’s ability to keep your transmission lubricated and help transfer power will be compromised. Changing your transmission fluid is an economical way to keep your systems at the top of their game and avoid complex, costly repairs.

Should I Change Transmission Fluid After 100k Miles?

Yes, you should change transmission fluid after 100k miles, but the type of transmission you have affects your ideal changing interval. If you have automatic, you can typically boost that range up to 60,000 to 100,000 miles. If you drive manual, most manufacturers will recommend changing your transmission fluid every 30,000 to 60,000 miles.

There’s no harm in changing your fluid early. Drivers with manual transmissions who put heavy-duty use into their vehicles may want to change their fluid every 15,000 miles. Likewise, changing your automatic transmission fluid every 30,000 miles may be necessary under some circumstances.

At the end of the day, consulting your owner’s manual or a trained technician is the best course of action to find the precise interval for your vehicle.

Why Does the Transmission Fluid Need to Be Changed?

Should I Change Transmission Fluid After 100k Miles

It mostly comes down to heat. Heat is the biggest killer of your transmission, partly because it’s the biggest killer of your transmission fluid. The fluid is not only a lubricant, but it also serves to prevent corrosion and actuate the clutches inside the transmission that perform the shifts. When heat breaks down the fluid, it loses some of its capabilities.

Excess heat can be generated by stop-and-go driving, hauling heavy loads or towing a trailer. For vehicles operating under “severe service” conditions, you should probably have the transmission fluid changed more often — as might be called for in the maintenance schedule.

Also, the clutch surfaces wear over time, and that creates debris. That debris is largely trapped by a filter that’s replaced when the fluid is changed.

Furthermore, it’s possible that the fluid level can get low, which can cause shifting problems. However, if the fluid is low, it’s likely because it’s leaking out somewhere, as it doesn’t just “burn off” as engine oil sometimes does. You can usually tell if transmission fluid is leaking, as you’ll see pink or red puddles on the ground — or maybe dark puddles if the transmission fluid is bad.

In any case, a transmission-fluid change, if done correctly, can address all of those issues.

What Happens If You Never Change Transmission Fluid?

The transmission fluid works as both a hydraulic fluid and a lubricant in an automatic transmission. Within that transmission, clutch packs reside. They include layers of friction substances.

That friction medium will keep the clutch or transmission from slipping. When you never change your transmission fluid or go too long between your transmission fluid changes, your transmission fluid will deteriorate and become less effective.

The friction material will also lose its effectiveness and wear off the clutch packs. Then, your transmission will likely begin to slip. If you haven’t ever replaced your transmission fluid and you’ve driven well over 100,000 miles (~160 934 km), the friction substance is probably floating around in your transmission fluid.

Now, if you merely change out your transmission fluid, you won’t remove all the friction substances from your transmission. Now, your car’s transmission will start to slip even more. That happens in a “drain and replace” filter and transmission fluid change. It also leaves a decent amount of the old fluid stuck in the torque converter and the transmission.

However, with a “drain and flush” method, the mechanic will have a machine drain and flush out all of the old transmission fluid. That way, all of the friction material floating around will get removed.

To avoid having these major vehicular problems, you need to pay attention to your owner’s manual and check the maintenance schedule. Get your transmission fluid changed at the right intervals based on the maintenance schedule. That will ensure your vehicle runs smoothly.

Otherwise, if you never change your transmission fluid, your transmission will start to slip. Your car won’t run as well.

Signs You Need to Change Transmission Fluid

The best way to know whether you need to change your transmission fluid is to check it yourself-or have a trained technician do it for you.  There are clear signs indicative of old, dirty transmission fluid. Here’s what you should be watching for.

  • Dirty transmission fluid
  • Transmission whining noise
  • Gears slipping
  • Can’t go into reverse gear
  • Slipping out of gear
  • Engine running hot
  • Grinding noise

If you notice these signals, get your vehicle to a service center right away to have your transmission fluid inspected and refilled if necessary. Here we explain in the right way How To Check Transmission Fluid.

The Benefits of Changing Your Transmission Fluid

Changing your transmission fluid is one of the most basic ways that you can extend the life of your car. Keep reading on below to learn about some of the great benefits you will experience by regularly changing your transmission fluid.

#1. Better Fuel Economy.

The idea of improving the fuel economy of our vehicles is certainly popular. Paying for gas is one of the biggest expenses associated with owning a car, so it makes sense that the majority of drivers are interested in finding a way to make their gasoline last longer.

Changing your transmission fluid regularly, especially when it has turned black, is a great way to improve your fuel economy. Your transmission will run smoother after you change the fluid, which means your engine will run smoother as well.

2. No Engine Lock-Up.

One of the worst things that can happen is engine lock-up. This essentially means that your vehicle’s transmission is working so hard that it simply shuts down

For many people, having their car out of commission can make a huge negative impact on their daily lives. You can avoid this unnecessary stress by regularly changing your transmission fluid.

3. Saves You Money.

Lots of people wait until their transmission is experiencing serious issues before they actually pay a professional to take a look.

This approach can lead to large expenses, as transmissions are complicated and delicate parts of our cars. By investing in regular transmission maintenance, which includes changing your transmission fluid, you can avoid the serious issues that typically come up without maintenance.

4. Car Runs Better.

By keeping your car transmission in top shape, you will notice a significant difference in the way that your car runs.

That means it will drive better, use less fuel, and be more effective with oil. Who doesn’t want a car that runs better? It doesn’t matter what make or model your car is, changing the transmission fluid is a necessary task for every car owner to take.


A transmission fluid change is a necessity for your vehicle and you will need to take a look at your owner’s manual to see when your automobile will need fresh transmission fluid. You may need to speak with your mechanic to see if there are any signs that your transmission fluid went bad. Dark brown and black transmission fluid has deteriorated and needs changing.

Make sure to keep your transmission fluid fresh and pursue maintenance in all other areas. If you do so, you will have a functional vehicle for many years to come.