Reviews

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

The best transmission additives for performance and efficiency.

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BY Heather Fishel / LAST UPDATED ON July 23, 2021

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
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Summary
Summary

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.

Pros
Pros
  • Features anti-friction metal treatment technology for treating metal surfaces
  • Restores responsiveness in transmission for smoother shifts
  • Ideal for both manual and automatic transmissions
Cons
Cons
  • 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 Overall
Prolong Super Lubricants PSL15000
Best Value
Lucas LUC10009
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Summary
Summary

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.

Pros
Pros
  • 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
Cons
Cons
  • Not ideal for faulty or damaged transmission systems
  • Dismal results with old, high-mileage vehicles 
Best Value
Lucas LUC10009
Honorable Mention
Hot Shot’s Secret HSSTSE32Z
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Summary
Summary

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. 

Pros
Pros
  • 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 
Cons
Cons
  • Not designed for manual transmission systems
  • Expensive compared to other additives in its range
  • Might not fix extreme hard shifting problems
Honorable Mention
Hot Shot’s Secret HSSTSE32Z

Benefits of Transmission Additives

  • Stop transmission leaks. Having a transmission leak might seem like a minor issue, but its aftermath could be profound. A small transmission leak could cause your transmission system to operate poorly. Transmission fluid is corrosive, so having small leaks could damage parts close by. Therefore, investing in a good transmission additive will help minimize leaks.
  • Minimize varnish and sludge formation. After extensive use, even high-quality transmission fluids begin to wear out and thicken. This happens when dirt and other contaminants mix with the fluid forming sludge. Thick fluid moves slowly, preventing the transmission parts from moving easily and efficiently. Getting proper treatment keeps your automatic transmission fluid (ATF) viscous, helping your transmission work as it should.
  • Reduce gearbox wear and tear. When gear oil moves throughout your vehicle’s transmission, it keeps your entire system working properly. However, when transmission fluid starts getting old, thickens, or forms impurities, your transmission will be forced to work harder and won’t be as effective. The harder your transmission system works, the more wear will be put on your auto parts.
  • Reduce transmission shudder and noise. When your transmission is working harder due to poor fluid, you will feel the effect not just in increased repairs but also in the noise that it makes. You will notice clacking, whirring, and other noises from your transmission. This will significantly reduce the quality of your ride. Adding a good transmission additive will help reduce the vibration and noises that you experience driving your vehicle.
  • Prolong the life of your transmission system. Getting the right additive will help extend the life of your transmission system. Purchasing the right transmission treatment for your car will help lower its running temperature and prevent overheating. It will also help reduce the wear on parts and keep your transmission running properly.

Types of Transmission Additives

Manual Transmission Additives

Manual gears operate on a system that has two shafts with gears. These gears mesh together after user input through the gear stick and clutch. As a result, the manual transmission system creates a lot of heat, friction, and force when the two moving objects come together. Due to this, manual transmission fluid, as well as additives, need to be able to make the gears transition as smooth as possible to prevent damage to components as they shift. To achieve this, manual transmission fluids are more resistant to heat, have high viscosity, and can function under extreme pressure.

Automatic Transmission Additives

Automatic transmissions operate in a planetary system. Gears switch automatically depending on the demands of the engine. Automatic gears tend to be smaller and have more moving parts compared to a manual gearbox. Therefore, the automatic transmission fluid, as well as additives, are on a different level than manual gearbox fluid. Automatic transmission additives have low viscosity and anti-foaming properties and are resistant to heat. 

Top Brands

Prolong Super Lubricants 

Prolong Super Lubricants is an American company headquartered in California that deals in the manufacturing, sale, and global distribution of a line of high-performance automotive lubricants. Prolong’s history is the perfect example of an American success story. The company was founded back in the 1990s. The founders operated from the back of a small shop packing the products themselves. Several years later, Prolong Lubricants Inc now sells millions of high-performance lubricants all over the world. The company’s products are based on an extreme pressure lubricant additive that is used for metal lubrication, commonly known as anti-friction metal treatment (AFMT). One of its popular products is Prolong Super Lubricants PSL15000.

Lucas Oil Products Inc

Lucas Oil Products incorporated is an American company that deals in the manufacturing and distribution of automotive lubricants and additives. The company was founded back in 1989 by Forrest Lucas and his wife, Charlotte. The company manufactures engine oils, gear lubes, greases, and car care products. Lucas Oil Products Inc markets about 270 automotive formulations in 40 countries. Its original plant and headquarters are in Corona, Calif. It opened a new plant in Corydon, Ind. in 2003. One of its popular products is Lucas LUC10009.

Lubrication Specialties Inc.

Lubrication Specialties Inc. is an American company that deals in blending and distribution of lubricants and greases. It was founded back in 1997 by Chris Gabrelcik. Lubrication Specialties Inc. offers automotive products such as aftermarket additives, industrial oils, gear lubricants, engine oils, food grade lubricants, crystal greases, and other lubricants. Lubrication Specialties Inc. is popular for resolving problems for some of the largest companies in North America, including America Showa, Nucor Steel, Midwest Industries, etc. One of its popular products is Hot Shot’s Secret HSSTSE32Z

 Best Transmission Additive Pricing

  • Under $10: There are a variety of transmission additives retailing at this price. However, most of the transmission additives only offer basic functionality. Depending on the manufacturing company, transmission additives here are popular due to their basic use and affordable price. 
  • $10-$30: The best transmission additives can be found at this price range. The transmission additives have much better composition and can be used for a wide range of applications, including transmission maintenance, heat reduction, valve lubrication, transmission failure, prevention of shudders, hard shifting, and power steering maintenance. 
  • $30 and up: There aren’t a lot of transmission additives over $30. Additives at this price bracket are premium products manufactured with high-quality materials for superior performance. They can be used for multiple applications, have good ratings, and offer the best results. 

Key Features

Transmission Compatibility

Start by checking your vehicle’s owner’s manual. It will show you what type of transmission fluid to use. Based on this information, you will be able to pick out the right additive. Using manual transmission additives on an automatic gearbox will have negative effects. Therefore, it’s essential that you check the product packaging for the right additive for your vehicle’s transmission system.

Transmission Fluid Type

Transmission fluids are available either in natural or synthetic forms, with synthetic transmission fluids being more popular on the market. It's important to find out what type of transmission fluid your system is using before purchasing an additive. Check the additive user instructions to find out if it is compatible with your transmission system’s fluid.

Additive Composition

The additive composition will determine the effectiveness of the product. Manufactures will use different ingredients to help boost the performance of their products. Getting a product with a good ingredient composition will offer better functionality and performance for your transmission. 

 Other Considerations

  • Quality. It's important to always stick to big brands and respected mid-sized company additives to ensure that you are getting premium products. It's tempting to buy cheaper import products or knock-offs, but they could end up costing more when you have to deal with transmission repairs.
  • Size. The bottle size often determines the number of times the product can be used. When it comes to lubricant additives, it's important to know the quantity of product that needs to be used for a single treatment. A high-capacity bottle can be used multiple times, saving money in the long run.
  • Formulation. Every transmission additive is different, with a different formula of ingredients. While they're all meant to help your transmission`s performance, each one offers a slightly different blend. And some even have more specialized benefits. For example, some additives are more concentrated; others are meant to reduce noise. Some additives are meant to prevent oxidation.
  • Suitability. Not all transmission additives are okay for all vehicles. In fact, using the wrong additive could actually void your car`s warranty, if you don`t choose carefully. To make sure the product you choose is okay for your specific make and model, double-check whether the additive's labeling mentions if it can be used on your car.


Best Transmission Additives Reviews & Recommendations 2021

Best Overall
Prolong Super Lubricants PSL15000

Prolong Super Lubricants PSL15000 additive is one of the best and most popular transmission additives on the market. This transmission additive 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. 

Best Value
Lucas LUC10009

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.

Honorable Mention
Hot Shot’s Secret HSSTSE32Z

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.

Honorable Mention
Lubegard 63010 Platinum Universal ATF Protectant

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.

Honorable Mention
Lubegard 19610 Instant Shudder Fixx

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.

Honorable Mention
XADO EX120 Revitalizant for Manual Transmission

This is a unique product that works to resolve a lot of issues in the transmission system. While reducing noise and vibrations, the additive also works to resolve hard shifting and ensure smooth transmission performance. We find it rather effective in manual systems, although some buyers even used it for CVT transmissions without any issues.


The best thing about this product is its versatility. XADO EX120 Revitalizant rebuilds, repairs, and protects metal parts and internal components in manual transmissions. Only one treatment with this product will last for 62,000 miles, which is rather impressive. On top of that, you'll get a tube with the gel and a syringe for easy application.


The tricky part is that you might have to wait for the product to work. Sometimes it takes time to resolve all the issues in the transmission system. You might even need to add the product to the fluid several times before noticing any changes. Therefore, if you need an additive that will work instantly, you might want to look for other options on our list.

Honorable Mention
ATP AT-222 Trans Fluid Additive

If you’re hoping to smooth out your transmission’s new habit of shuddering, you’re going to want to pick up ATP AT-222 Trans Fluid Additive. This product is specifically formulated to tackle problems — specifically, a shuddering transmission — head on. It’s a highly concentrated additive that’s formulated as a synthetic friction modifier, which works to stop the transmission’s torque converter’s potential shudders. And thanks to the highly concentrated ingredients, you’ll get resolution for your problems fast. This quick-working, super concentrated additive is compatible with all kinds of automatic transmissions, so it’s safe to use regardless of your vehicle’s make and model. 


There are a few drawbacks to its formula, however. Unlike more general or universally applicable products, this particular transmission additive doesn’t include any enhancements. It won’t reduce transmission heat, cut back on wear, or even extend the life of your transmission fluid. It’s merely meant to provide you with a solution rather than a general salve.

Honorable Mention
Lubegard 67010 CVT Recharge & Protect

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.

Honorable Mention
Sea Foam TT-16 Trans Tune Transmission Additive

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.

Honorable Mention
K & W Chemical Trans-X High Mileage Automatic Transmission Treatment

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.

Tips

  • 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.
  • Before adding a transmission additive, you first need to warm up your vehicle’s engine and transmission to operating temperatures. Have your car idle for 20 to 30 minutes.
  • Read the instruction label on your additive before adding it to your system. Depending on the additive, you might only require one bottle. However, two might be necessary for larger vehicles.
  • Before adding some transmission additive, 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.

FAQs

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 additive?

Transmission additives are best used 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 episodes of rough transmission shifting, slipping, or hesitation, it is 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’re experiencing transmission issues and you choose an additive that’s specifically formulated to tackle those problems, you can see positive results. However, 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.

Final Thoughts

Our pick for the best transmission additive is the Prolong Super Lubricants PSL15000. It is one of the best transmission additives on the market. It reduces leaks, shudders, slippage, and sludge buildup.

For a less pricey option, consider the Lucas LUC10009.