Best Transmission Additives: Restore Your Transmission’s Health for Smoother Performance

The best transmission additives for performance and efficiency.

byHeather Fishel|
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BYHeather Fishel/ LAST UPDATED ON May 10, 2023

Has your car’s transmission suddenly started acting up? Is it shuddering while you’re on the road, or putting you through harsh, uncomfortable changes you can feel from behind the wheel, it’s time to check out what’s happening under the hood. Problems like these could mean your transmission is in need of repairs. But it could also indicate an issue with your transmission fluid. While you might not think about your car’s transmission fluid very frequently, it’s a small part of your vehicle’s most critical system.

And in order to work smoothly and deliver great performance, you need transmission fluid for proper lubrication and function. If your transmission fluid isn’t at the right level – or if you’re using the wrong type — big problems can happen. Fortunately, you can easily maintain both your transmission and your transmission fluid with a transmission additive. Designed to protect the transmission while improving its performance, an additive can be a particularly handy tool. Wondering if you could benefit from one? We have the best transmission additives available right here, along with a guide to help you find the right fit for your vehicle.

Best Overall
Prolong Super Lubricants PSL15000

Prolong Super Lubricants PSL15000

Prolong Super Lubricants PSL15000 is a trusted additive that works for both manual and automatic transmission systems. Manufactured with a unique formula that protects against friction and heat.
  • Features anti-friction metal treatment technology for treating metal surfaces
  • Restores responsiveness in transmission for smoother shifts
  • Ideal for both manual and automatic transmissions
  • Not designed to work with CVT transmission systems
  • Performs poorly with high-mileage SUV and trucks
  • Tiny bottle
  • Hard to use with a standard funnel
Best Value

Lucas LUC10009

Lucas LUC10009 Transmission Fix is an affordable, 100-percent solvent-free additive that has been specially designed for slipping transmission issues. Features a polymeric film that renews bands to stop seal leaks.
  • Eliminates slippage issues
  • Offers the perfect balance between price and performance
  • Comes in a 24-ounce bottle for multiple uses
  • Prevents foaming
  • No need for AFT flush or draining when using this additive
  • Not ideal for faulty or damaged transmission systems
  • Dismal results with old, high-mileage vehicles
Honorable Mention

Hot Shot’s Secret HSSTSE32Z

Hot Shot’s Secret HSSTSE32Z is a high-performance transmission additive specially formulated for automatic transmission systems, including CVT transmissions. Ideal for temperature reduction and pulling deposits from coated areas.
  • Ideal for both gas and diesel automatic transmission vehicles
  • Comes in a large 32-ounce bottle for multiple uses
  • Offers quick results
  • Reduces friction and wear
  • Not designed for manual transmission systems
  • Expensive compared to other additives in its range
  • Might not fix extreme hard shifting problems

Summary List

Honorable Mention

Our Methodology

To select these products, we weighed how price, benefits, and application came together for each and denoted as necessary. If a transmission additive has few benefits but commands a reasonable price, it's not necessarily a bad product. On the other hand, if a product is on the more expensive side and also has few benefits (especially in user review form), then that's not as ideal.

We also cover a wide variety of transmission additives, meaning ones that could either work in conventional, torque-converter automatic transmissions, manual transmissions, and CVTs (or all of the above). Then, whether the additive plays nice with conventional petroleum-based or synthetic transmission fluid.

For more info on our methodology, check this out.

Best Transmission Additives Reviews & Recommendations

Prolong Super Lubricants PSL15000 additive is one of the best and most popular transmission additives on the market. This option can be used for both manual and automatic transmission systems. Prolong Super Lubricant works by producing molecules that interact with metal surfaces. These molecules create a protective layer that reduces heat and friction within the transmission system.

The PSL15000 promotes smooth and responsive gear changes, and it is suitable for both high- and low-mileage vehicles. A single 8-ounce bottle of Prolong Super Lubricants Transmission Additive will treat a complete transmission. This additive’s formula includes AFMT that chemically bonds to the surfaces of your system, providing a protective layer that helps reduce wear and tear. 

A drawback to this product is that it has not been designed to work with CVT transmission systems. This product doesn’t work as efficiently with high-mileage SUV and trucks. 


Noticeable benefits include smoother shifts, less noise, and reduction in shuddering

Good price

One small bottle is all it takes for most transmissions


Does not work with CVT transmissions

Does not work with high-mileage and older vehicles

Lucas Lubricants produce some of the best additives on the market that have a reputation for great results. The Lucas LUC10009 is a relatively new product on the market but still offers amazing performance and is highly recommended for transmission problems, such as slipping transmission, leakages, and hard shifting issues. It offers the perfect balance between price and performance.

The LUC10009 is a 100 percent solvent-free formula that has been designed to prevent foaming. It also helps lower the operating temperature of the fluid, stopping seal leaks. You can use this formula to revitalize old or worn-out transmission fluid—there is no need for draining. The Lucas Super Lubricants LUC10009 comes in a 24-ounce bottle. It can be used for multiple treatments.

The greatest benefit users can get is it forms a polymeric film that works by renewing worn bands that help prevent transmission slippage. This process prevents overheating, renewing fluid that becomes worn due to heavy hauling. The LUC10009 is one of the best transmission additives for slippage.

One downside is this transmission additive might not work well with a faulty or too far gone transmission system. It will also not improve performance on severely worn out transmission systems.


Good price for the size of the bottle

Easy to use

Can be used to replenish existing fluid


Will not breathe new life into a broken or very tired transmission

Some users report very little difference after use

If you have a diesel-powered engine and you can’t find a suitable transmission additive, then Hot Shot’s Secret HSSTSE32Z is your best bet. This ATF additive is suitable for both gas and diesel automatic transmission systems. It is an ideal transmission additive if you are looking to soften up your shifts, create a smoother ride, and protect your transmission.

The HSSTSE32Z helps lower ATF temperatures, reduces friction, and eliminates rust and corrosion, improving the overall performance of your automatic transmission system. A bonus with Hot Shot’s Secret Transmission Additive is it also works with CVT transmissions. It is a high-formulation lubricant with a unique composition capable of pulling deposits from coated areas.

A big drawback to the Hot Shot’s Secret HSSTSE32Z is that it can only be used with automatic transmission vehicles. It’s also pricey compared to other transmission additives. However, you get more benefit from its 32-ounce bottle.


Works in conventional and CVT automatic transmissions

Eliminates slips and shudders

Eliminates any rust and reconditions seals


Cannot be used in manual transmissions


Lubegard offers a budget-friendly and reliable product you can use along with automatic transmission fluids. It's a rather efficient product that reduces friction and protects metal parts and internal components from damage. Furthermore, the additive works to prevent overheating without damaging the transmission system.

Thanks to the Synergol TMS Technology, the additive eliminates shudder and noises, making your rides more enjoyable. Another great thing about this additive is the ability to protect, condition, and restore seals and O-rings. It also prolongs the need to change the transmission fluid, which is rather convenient. For all the mentioned reasons, the Lubegard ATF protectant is one of the favorite choices among mechanics and drivers. The extra reason might be that the additive works on most automatic transmissions.

Despite the claims of universality, though, the additive won't work on just any type of vehicle. It's not recommended for CVT transmissions that most new cars and old Ford ones have. To make sure the product will work on your system, you have to go to the company's website and check out the provided comparison chart.


Lubricates, protects, and conditions O-rings and seals

Prolongs fluid life

Reduces friction inside the transmission for smooth operation


Not recommended for CVTs or Ford vehicles

It's a good idea to examine the company's application list before buying

Here’s another product specially designed for automatic transmission fluids. It's formulated to reduce and eliminate shudder, but it also works to resolve other transmission issues. Along with fixing the noise that makes rides uncomfortable, the additive makes fluids work for longer and enhances their overall performance.

The reason why both DIYers and professional mechanics opt for this product is the overall versatility and convenience. The additive is compatible with all synthetic automatic transmission fluids and proves to be rather efficient. The application is simple, and the product comes at a reasonable price. Therefore, drivers can protect, maintain, and repair the transmission system without much effort at all.

The bottle design is a little awkward, though. It's difficult to handle and might be challenging to pour the liquid from it. Still, the bigger issue regards the somewhat inconsistency the product might show over time. We noticed that the additive doesn't always reduce chatter and noise to desired levels. It mostly depends on vehicle and transmission system types.


Compatible with all synthetic transmission fluids

Reduces noise

Eliminates shudder


Inconsistent benefits among users

Awkward bottle design

This Lubegard product is ideal for those who are searching for CVT transmission additives. It's reliable, efficient, and budget-friendly. With just one application, the additive makes a huge difference in the transmission. From repairing damage to preventing it, the Lubegard additive works on all kinds of issues.

This particular additive doesn't only reduce noise and shudders. It also protects engine belts, pulleys, and other components. The additive will help you prevent premature wear of internal parts and damages caused by degraded fluid. In general, it will enhance the performance of your vehicle, making rides more comfortable and quiet.

There are only two minor drawbacks to keep in mind before the purchase. Firstly, the product doesn't always completely reduce the noise. It makes shifting incredibly smooth, but some shudder might remain even after the application. Secondly, you might have to wait for the additive to show results, although this mostly depends on the vehicle model.


Specially formulated for CVT transmissions

Excellent price

Reconditions fluid that's already in there


Cuts down on noise but doesn't reduce shudder

It might take time for benefits to show up

Looking for a transmission additive that can do it all? You’ll love the Sea Foam TT-16 Trans Tune Transmission Additive. Designed to fine-tune your transmission, its fluid, and its overall performance, incorporating this under the hood can help round out your vehicle’s on-road results. And you may even be able to avoid future issues.

Sold in a 16-ounce aerosol can, Sea Foam’s additive features a petroleum base and three different oils, all blended together to clean deposits throughout your transmission and its related systems. It can be used in all petroleum and synthetic hydraulic fluids — which means it’s safe for just about any automatic transmissions. 

Once applied, this additive can help reduce rough, erratic shifting, eliminate contamination, and clean up your transmission overall. It works like a system flush, cleaning and clearing to remove potentially damaging contaminants, deposits, and moisture. And it won’t harm any seals or your transmission fluid along the way.


Aerosol spray makes adding to transmission easy

Works in all petroleum-based and synthetic fluids

Cleans deposits and lubricates components


Adding it to the transmission can be messy

Higher price than other options

If you drive an older car with many, many miles on its odometer, you’ll want to consider K & W Chemical Trans-X High Mileage Automatic Transmission Treatment. This transmission additive is specially formulated and developed for cars with at least 75,000 miles, and it’ll work on much higher mileages, too. Each 16-ounce container of this additive can extend the lifespan of your current transmission, helping you to avoid common problems that can come with a whole lot of driving.

Made with a high-tech formula that’s designed to protect and bolster your transmission, this additive can stop or prevent leaks. It’s also a great option if you’re noticing less-than-smooth shifting; it can bring back the smoothness your vehicle once delivered. And adding this into your transmission fluid’s mix can also help replace any depleted ingredients it might’ve lost over time.

However, you’ll want to keep in mind that this additive is best used if you’re just starting to experience transmission issues like slips and shudders. It won’t be nearly as effective if you’re already seeing persistent problems.


Specially formulated for transmissions with higher mileage

Cuts down on shifting and driveability issues

Convenient, easy to use bottle


Only effective at the onset of shuddering and shifting issues

A pricier option than others

Our Verdict on the Best Transmission Additives

Lucas LUC10009 takes the cake as our top choice. It's a solid mix of value, benefit, and ease of use. Most additive instructions say that you can add the transmission conditioner to the existing transmission fluid. However, it's recommended that you check the fluid levels first. This is to ensure you don’t overfill.

Then, before adding some, make sure you locate the right dipstick. In case you are uncertain of its location, check online or in your vehicle owner’s manual. Remove the dipstick and use a funnel to channel the additive into the system.

After adding the additive, it's recommended that you drive your vehicle for a while, shifting through all the gears.


Q: Can I add transmission additive myself?

Yes, you definitely can take the DIY approach. Just make sure you locate the transmission dipstick. With little preparation, this is a task you can complete in a few minutes. Make sure you carefully read both your vehicle owner’s manual and the additive user instructions.

Q: When is it ideal to use transmission additives?

Transmission additives are best if you are experiencing transmission slippage, stalling, rough shifting, or seal leaks, and you want to try a cheaper option before resorting to a repair shop.

Q: Should I add a transmission additive when changing transmission fluid?

Unless you have been experiencing rough transmission shifting, slipping, or hesitation, it's not recommended that you add transmission treatment.

Q: Do transmission additives really work?

The answer to this question depends on a few different factors. If you use an additive without having any issues, or if your car is newer, you may not really see any effect. In certain cases, additives can do more harm than good, so make sure to do thorough research before adding anything into your transmission fluid.

Q: What transmission additives work for slipping?

If your car’s transmission is slipping, you’ll want to find an additive that’s specifically formulated for this kind of problem. While some are formulated to clean your transmission and its components, others are made to target issues just like slipping and shuddering. Highly concentrated formulas can work fast, but make sure to double-check the label to make sure that’s the case with the additive you pick.

Why Trust Us

Our reviews are driven by a combination of hands-on testing, expert input, “wisdom of the crowd” assessments from actual buyers, and our own expertise. We always aim to offer genuine, accurate guides to help you find the best picks.

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