Home FAQ

Is 100,000 miles too late to change transmission fluid?

The short answer is no, it's generally not too late to change the transmission fluid in a vehicle with 100,000 miles or more. While it's best to follow the manufacturer's recommended service intervals, changing the fluid can still be beneficial even at higher mileages.

Understanding Transmission Fluid Maintenance

Transmission fluid plays a crucial role in the proper functioning of a vehicle's transmission. Over time, the fluid can break down, become contaminated, and lose its lubricating properties. This can lead to increased wear and tear on the transmission components, potentially causing problems down the road.

Most manufacturers recommend changing the transmission fluid every 30,000 to 60,000 miles, depending on the vehicle and driving conditions. However, many people neglect this maintenance, leading to the fluid becoming old and degraded.

Benefits of Changing Transmission Fluid at 100,000 Miles

Even if a vehicle has reached the 100,000-mile mark, changing the transmission fluid can still be beneficial. Some of the key advantages include:

Improved Transmission Performance: Fresh transmission fluid can help restore the transmission's smooth operation, reducing the risk of shifting problems, slipping, or other issues.

Extended Transmission Life: Replacing the old, contaminated fluid with new, clean fluid can help extend the life of the transmission, potentially preventing costly repairs down the line.

Reduced Wear and Tear: The new fluid provides better lubrication, reducing the wear and tear on the transmission components and helping to prevent premature failure.

Increased Fuel Efficiency: Properly maintained transmission fluid can improve the vehicle's overall efficiency, leading to better fuel economy.

It's important to note that the specific recommendations may vary depending on the make, model, and year of the vehicle. Consulting the owner's manual or a trusted mechanic is advisable to ensure the proper fluid type and service interval is followed.

What fluids need to be changed at 100k miles?

At 100,000 miles, you should replace engine oil and filter, transmission fluid, coolant, and brake fluid, as these fluids break down over time and can cause damage to critical components. You should also consider replacing spark plugs and the timing belt, which can fail and cause serious engine damage.
This video explains why it's important to change transmission fluid after 100,000 miles: 39sCar Care ProYouTube · Sep 6, 2025
Essential fluids

Engine oil and filter: Oil breaks down and becomes contaminated with metal shavings and carbon deposits, which can accelerate wear on engine parts. A new filter ensures clean oil circulates properly.
Transmission fluid: This fluid lubricates the transmission gears. Over time, it breaks down and can become contaminated, so it needs to be flushed and replaced to prevent premature wear.
Coolant: Coolant can lose its ability to prevent corrosion over time, even if its heat transfer capability remains. Replacing it at this mileage is crucial for protecting the system.
Brake fluid: Brake fluid absorbs moisture, which can lead to corrosion in brake components like the ABS module and calipers. Flushing and replacing it is essential for safety and to prevent costly repairs.

This video explains why it's important to change brake fluid after 100,000 miles: 1mRQs GarageYouTube · Jul 26, 2022
Other important maintenance

Timing belt: A timing belt replacement is often recommended around 100,000 miles. A broken timing belt can cause severe internal engine damage.
Spark plugs: At this mileage, spark plugs may be worn and should be checked and replaced if necessary.
Power steering fluid: If your vehicle has hydraulic power steering, the fluid should be inspected and replaced as recommended by the manufacturer, as it may need service around this time.
Differential and transfer case fluids: For vehicles with a 4WD or AWD system, these fluids should also be checked and replaced according to the manufacturer's schedule.

This video explains why it's important to change fluids after 100,000 miles: 57sTire ReviewYouTube · Aug 28, 2024
Important note

Always consult your vehicle's owner's manual or a professional mechanic to determine the exact service intervals and fluid types for your specific car.

Why do people say never change transmission fluid?

The saying "never change transmission fluid" is a myth, but there's a kernel of truth to it when the fluid is neglected for a very long time. If a transmission has never had its fluid changed and the fluid is dark and burnt, new fluid can dissolve the "varnish" and debris that have been acting as a temporary sealant for worn parts, potentially causing the transmission to slip or fail.
This video explains why changing transmission fluid can be beneficial: 57sScotty KilmerYouTube · May 11, 2023
Why the misconception exists

Worn-out fluid: Over time, transmission fluid breaks down and can accumulate debris and "varnish" from worn internal components.
Temporary "fix": In a high-mileage, neglected transmission, this old, grimy fluid may have been holding worn parts together, acting as a makeshift sealant.
The risk of a flush: A full transmission flush, which uses high pressure to force new fluid through the system, can dislodge this built-up material and potentially cause seals to fail or clutch packs to slip, leading to a more expensive repair.

What to do instead

Regularly change fluid: The best practice is to follow your vehicle manufacturer's recommended service intervals for changing the fluid.
Drain and fill: If your car has high mileage with unknown fluid history, a "drain and fill" or "pan drop" is safer than a full flush.
Focus on the pan drop: This method removes only a portion of the old fluid and allows for the filter to be changed and the magnet to be cleaned.
Use new fluid carefully: Adding new fluid can still be beneficial, even in older transmissions, but be aware of the risks if the fluid is extremely degraded.
Don't ignore signs of failure: If the fluid has a burnt smell or contains metal flecks, it indicates a problem, and a fluid change may not be enough.

This video explains how to safely change transmission fluid: 53sScotty KilmerYouTube · Jun 8, 2021

Is it bad to change transmission fluid at 100k miles?

Depends on how many miles on you car. If you have around 50000 miles on it you can have it flushed out and changed your transmission filter and fluid. If you have 90 to 100000 miles i would not have it flushed out because the pressure would blowout the rubber o-rings and any other rubber parts.

Can it be too late to change transmission fluid?

It is not too late to change transmission fluid, even on older or high-mileage vehicles, but it can be risky if the fluid has never been changed before. A full, aggressive flush on a neglected transmission can dislodge large amounts of debris and cause slipping or failure, especially if the transmission is already worn. For older vehicles with over 100,000100 comma 000100,000 miles that have never had the fluid changed, a less aggressive "drain and fill" with a filter change is often the recommended approach, and some recommend adding an anti-slip additive or even just changing the filter and reusing the old fluid.
When to proceed with caution

If the vehicle has over 100,000100 comma 000100,000 miles and the fluid has never been changed, be aware that the old fluid may contain debris and clutch material that helps the transmission grip.
An aggressive flush can dislodge this debris all at once, potentially clogging passages or causing slippage.

How to change the fluid in an older vehicle

Perform a drain and fill: This method replaces only a portion of the fluid and is less likely to cause issues than a full flush.
Change the filter: It is a good idea to change the filter during this service.
Consider an anti-slip additive: Some mechanics suggest replacing a quart of the old fluid with an additive, or adding an additive after the fluid change to help improve performance.
Just change the filter: In some cases, a less invasive approach is to simply change the filter and put the old fluid back in, which can sometimes help with performance issues.
Be prepared for the possibility of failure: If the transmission is already failing, changing the fluid may not save it and could even accelerate the problem.

What to do if you are not sure

Check your owner's manual: The manual will have the manufacturer's recommended service intervals.
Look for signs of a problem: If your transmission is shifting roughly, slipping, or making whining or grinding noises, it's a good idea to get it checked out, even if you are unsure about the fluid change.
Get a fluid analysis: A professional can analyze your old transmission fluid to determine its condition and whether a change is necessary.

Kevin Bennett

Company Owner

Kevin Bennet is the founder and owner of Kevin's Autos, a leading automotive service provider in Australia. With a deep commitment to customer satisfaction and years of industry expertise, Kevin uses his blog to answer the most common questions posed by his customers. From maintenance tips to troubleshooting advice, Kevin's articles are designed to empower drivers with the knowledge they need to keep their vehicles running smoothly and safely.