Best Transmission Fluids and Additives for Your Vehicle

Did you know that sporadic flushing of transmission fluid is probably the #1 cause for serious gearbox issues? If not, then you are most certainly aware of how costly transmission repairs can be. Transmission fluids and additives are crucial for the smooth operation of your vehicle and changing them on a regular basis will reduce the wear on parts.

Such fluids are mostly used for vehicles with automatic transmissions, but they can also smooth out the manual gear change. So, don’t shy away from using them if you prefer to drive stick.

Even though their purpose is similar, automatic transmission fluids and additives are actually two different things. With the right viscosity, automatic transmission fluids (ATF) dissipate heat in vehicles and lubricate bearing surfaces. Also, they are based on oil and may contain certain additives that improve lubrication.

The purpose of additives, on the other hand, is to reduce friction to a minimum. However, they can have other purposes too, such as improving the viscosity of ATFs, as well as protecting and cleaning metal surfaces. Moreover, they can ease up difficult shifting and remove weird noises and strange shudders that sometimes appear.

In any case, if you use both of these liquids, you will most certainly prolong the life of your transmission and help your vehicle shift effortlessly. The bad news is that these fluids are not omnipotent. Sometimes, you’ll simply have to break the bank and replace the gearbox no matter what.

Why You Need Transmission Fluids

A vehicle’s engine can generate heat so intense that can lead to transmission overheating and eventually a complete breakdown. Using transmission fluids is the only way to prevent this.

Transmission fluid cools down your gearbox so that it can work properly. Moreover, it also serves as a lubricant, just like car oil by reducing friction and preventing parts from grinding against each other. In other words, a good transmission fluid prolongs the life of the whole transmission system.

Unfortunately, transmission fluids won’t last forever. Over time, they collect small metal particles that can cause a complete transmission breakdown. As soon as the color of the liquid changes, know that it was contaminated by such debris.

Moreover, the heat will eventually break down the chemical components of transmission fluids, no matter how good they are. They won’t lubricate nor cool as well as they used to and the transmission will start to wear off.

Therefore, in order to avoid costly gearbox repairs, make sure to inspect your transmission fluids on a regular basis, and change them when needed.

How to Pick the Right Fluid for Your Car

If you own a car manufactured before 2006, you will probably have a limited range of available transmission fluids at your disposal.

The good news is that you don’t have to think too much about whether a certain fluid is right for your vehicle. The bad news is that you might not have any other option if you’re not satisfied with the price or performance of your current fluid.

But how do you pick the right one if your vehicle was made after 2006?

You won’t make a mistake if you buy the brand that was recommended by your car’s manufacturer. In contrast, you can opt for some cheaper aftermarket variants that you can purchase online or from auto parts dealers.

If the seller asks you whether you want a traditional or a synthetic fluid, know that it’s OK to pick either of the two. The only important difference is that traditional fluids are usually less resistant to friction and heat than synthetic ones. So, if you plan to put a huge amount of pressure on your gearbox by towing a trailer, make sure to go with the synthetic option.

In order to make things easier for you, I’ve put up a compatibility list of the most common transmission fluid types and different vehicle models.

• SP IV — Kia, Mitsubishi, Hyundai
• ATF-TIV — Some but not all Audi, Volkswagen, Toyota, and Lexus
• ATF-WS — 2004 Toyota and later
• ATF DW-1 — Honda and Acura except for models with the CVT gearbox
• ATF+4 — Chrysler, Dodge, Jeep
• Matis S, Matis D, Matis K — Nissan, Infiniti, Subaru
• Mercon V — Lincoln, Mercury, Ford
• Mercon LV — Mazda, Ford
• Dexron VI — GM and pre 2004 Toyota

6 Best Transmission Fluids on the Market (2023)

1. Mobil 1 Synthetic Automatic Transmission Fluid

Even though Mobil 1 Synthetic ATF isn’t the cheapest product out there, it will last longer than alternatives that are less expensive. This fluid has an exceptional viscosity which allows it to withhold high temperatures for a long time without thermal breakdown.

As long as Mobil 1 Synthetic ATF is in pristine condition, it will cool down the transmission to a great extent. With it, there are no chances for overheating. Moreover, it will improve the overall cleanliness of the gearbox, even in severe driving conditions such as heavy traffic, hot temperatures, and towing.

Needless to say, Mobile 1 performs great at extremely high temperatures. But will this product thicken if you’re living in a cold climate where temperatures usually drop below zero? Absolutely not.

The manufacturer claims that this fluid provides an amazing performance at temperatures as low as -65.2 ºF. To be honest, I’ve never met a driver from Alaska that has used it, but I believe that the manufacturer wouldn’t make such a strong claim if it wasn’t true.

Mobile 1 Synthetic ATF will work with most Ford and GM models. Yet, it is also compatible with most modern high-performance cars, SUVs, vans, SUTs, and other light trucks. Finally, even though it might be a bit pricey, this transmission fluid won’t let you down even in most extreme weather conditions.

Main Features:

• Provides optimal performance at temperatures as low as -54 °C
• Has a high viscosity index of 176
• Stable at extremely high temperatures
• Cools down the transmission to a great extent
• Promotes quiet shifting

2. Royal Purple Max High-Performance Automatic Transmission Fluid

Royal Purple Max High-Performance ATF is one of the most reputable brands in the automotive industry. Aside from other world-class products, their ATFs are also exceptional.

What makes this transmission fluid stand out from the rest is its compatibility with other liquids. In other words, you don’t have to worry if you pour it into some other ATF. It won’t cause any problems with your transmission. However, you will get the best performance out of it only if you completely drain the ATF you currently have in your vehicle.

Due to its high film strength, Royal Purple Max can reduce the transmission heat up to 20 ºF. It also reduces the wear on parts. Such reduction will double the life of any transmission out there.

Moreover, thanks to good viscosity, this ATF is stable at high temperatures. So, you won’t have to change it as frequently as some other, less expensive variants. That can reduce the cost of transmission maintenance, and you’ll visit your mechanic less frequently.

Generally speaking, Royal Purple’s Max ATF is compatible with different vehicle models that range from BMW to Chrysler, Suzuki, and Kia. However, make sure to check the compatibility information provided by the manufacturer before you buy it.

Main Features:

• Compatible with different ATFs
• Maintains great viscosity at extreme transmission temperatures
• Works with most ZF automatic transmissions
• Compatible with most European car models
• Has similar specs as Mercon V, ATF+4, Dexron III, and others

3. Valvoline MaxLife

Valvoline MaxLife is another awesome product that is based on group III paraffinic oil. It’s recommended for most GM, Toyota, Honda, and Ford models as well as vehicles that require fluids with Dexron VI, Mercon V, and even Mercon LV specs. However, you shouldn’t pour it in your vehicle if it requires ATF+4 or if it has a CVT transmission.

MaxLife is synthetic, which means that you don’t have to change it that often. It’s also quite stable and will maintain its viscosity even in extreme temperatures. With this fluid, you wouldn’t have to worry about transmission breakdown — your gearbox will remain cool enough even in severe driving conditions.

Valvoline’s MaxLife is quite popular among drivers because it incorporates additives that prevent leaks. It also has additives that clean debris that was caused by excessive friction. Due to them, this fluid reduces shudder to a bare minimum.

This ATF is probably one of the most efficient inexpensive options on this list. Due to its prolonged life, you will be able to save a considerable amount of money. And if your car is compatible with its specs, you should definitely give it a try.

Main Features:

• Synthetic base oils
• Lasts longer
• Includes cleaning agents and agents that prevent leaks
• Available for a wide range of car models

4. Castrol Transmax

Castrol is a well-known brand in the automotive industry with products that are highly acclaimed across the globe. Aside from top-notch car service parts and different liquids like oil, they also offer state-of-the-art automatic transmission fluids.

Unlike other Castrol’s ATFs that are based on mineral oil, the Transmax fluid is completely synthetic. Such fluids tend to perform better in towing vehicles than mineral ones.

What’s also great about Transmax is that it is a lot cheaper than other products that offer the same characteristics. Therefore, if you were looking for a budget option, you should at least check this ATF out.

This product has different versions that meet different requirements. For example, some of them are optimized for Dexron VI specs, and some for ATF +4 or Mercon V. But the base version satisfies the Mercon, Dexron, Dexron-III, IIE, and II.

In other words, there are enough options to satisfy owners of Japanese, European, and even some older American vehicles.

Above all, Castrol Transmax provides incredibly smooth shifting. As a driver, you will be able to see the difference in so much as an instant, especially if your current ATF isn’t that satisfying. Moreover, you can also use it with vehicles that have power steering and where Mercon specs are mandatory.

Finally, I don’t believe there’s anything else left to say about a durable ATF that has outstanding performance and even comes at a great price. It seems that Castrol has really become a synonym for world-class products that are also affordable. I wholeheartedly encourage you to try out Transmax sometimes in the future.

Main Features:

• Low Price
• Meets a wide range of OEM specs
• Provides smooth gear change
• Excellent thermal protection due to additives

5. ACDelco

Not all ATFs on the market can meet the Dexron VI specs. As a result, owners of vehicles that have such requirements are faced with a limited number of options to choose from.

ACDelco is one of the best Dexron VI fluids out there, and it also provides a good value for money. It may not be as cheap as the Castrol’s version, but if you’re looking for a world-class alternative — ACDelco is the way to go.

Moreover, this fluid is also compatible with previous Dexron requirements. So, you will be able to use it as an alternative fluid for most vehicles with older transmission types.

The effects of using this ATF are simply outstanding. Due to ACDelco’s stable viscosity, the shifting performance will become more consistent even in extreme driving conditions. Also, ACDelco is quite durable and will last long even if you tow a trailer every single day. It’s resistant to oxidation and provides exceptional aeration and foam control.

ACDelco is licensed and approved by General Motors, and they recommend it for all GM vehicles from 2006 and newer. With that being said, it’s no wonder why it’s one of the most popular automatic transmission fluids in the USA.

Main Features:

• Compatible with older Dexron specs
• Great stability
• More durable than some others
• Resistant to oxidation
• Provides better shifting performance

6. Red Line D4 Automatic Transmission Fluid

No matter how good they are, most ATFs will thicken at low air temperatures and cause transmission problems. Yet, there are some liquids that maintain their viscosity even when temperatures drop below zero.

Red Line D4 Automatic Transmission Fluid provides effortless shifting for your gearbox even at low temperatures. With this liquid, you won’t feel a difference between driving on a hot summer day and a freezing winter night. Gear changing will be smooth, and it will remain consistent as long as D4 lasts.

Also, it has superior stability when compared to its petroleum counterparts. As a result, with Red Line D4, there are fewer chances for transmission overheating.

D4 is versatile. Aside from different vehicles, you can use it both for manual and automatic transmissions. However, there are other exceptional Red Line fluids for cars that need better performance. For example, there’s High-Temp ATF for towing vehicles and Racing ATF intended for all drag racing enthusiasts out there.

Whatever option you chose, you can rest assured that Red Line’s products are durable and provide a great value for money. You simply can’t go wrong if you decide to try them out.

Main Features:

• Great performance at low temperatures
• Stable at high temperatures
• Provides consistent shifting during its lifetime
• Affordable
• Supports both manual and automatic transmissions

Are Transmission Additives Effective?

Some additive manufacturers go over the top by claiming that their products can solve all transmission problems. Such claims cause wariness among drivers because no one is that naive to believe that a liquid can repair something broken.

However, such liquids are helpful and can aid the gearbox to run smoothly and even prolong its life.

For example, when a transmission wears out, the internal seals harden and crack. Such seals won’t contain the pressure behind them and will cause leaks and even shifting delays. If you mix additives with your transmission fluid, they will soften those seals and make them work properly again.

Yet, you shouldn’t consider them as long-term fixes. If you are experiencing persistent problems when shifting, make sure to visit your mechanic. In some cases, shifting problems are caused by broken internal seals. And if they’re not repaired ASAP, you will end up with a transmission breakdown.

Benefits of Transmission Additives

Aside from stopping leaks, transmission additives have other benefits too. For example, transmission fluids thicken over time. Dirt and debris mix with them and prevent them from moving as they should. As a result, gearbox parts will start decaying.

Proper additives keep the fluids viscous and stop the impurities from piling up. By doing so, they also reduce noise and shudder. Moreover, they can lower the temperature of your transmission and prevent overheating.

The transmission will again work effortlessly, and its parts will last longer. Simply put, additives can save you from frequent trips to the mechanic and prolong the life of your gearbox.

Here’s a summary of all that additives can do for your vehicle:

• Stop or reduce leaks
• Keep the transmission fluid viscous
• Reduce shudder
• Reduce noise
• Extend the life of the transmission

6 Best Transmission Additives on the Market (2023)

1. Lucas 10009 Transmission Fix

Lucas Transmission Fix does exactly what its name says. Even though it can’t substitute a real mechanic, it will do wonders with slipping transmissions. But that’s not all. This additive can do so much more and you can either use it to solve transmission problems or to prevent them.

Above all, Lucas Transmission Fix is convenient. You don’t have to drain all transmission fluid from your vehicle first — you can simply mix this product with any ATF that’s already there. However, I would recommend changing your ATF before you do, if you want to get optimal results.

Lucas Transmission Fix has multiple benefits. It can stop the fluid from foaming, dry up leaks, and lower the transmission temperature. As a result, this product will minimize the chances for overheating.

Most importantly, Transmission Fix will help to stop transmission slipping. Once you pour it in your car, the shifting will become smooth once again, and there will be no hesitation between gears.

The product is recommended mainly for manual transmissions, but you shouldn’t use it if your vehicle has a CVT one. What’s also amazing is that Lucas Transmission Fix comes at a great price. Therefore, it can save you a ton of money that you would spend on fixing your transmission after a breakdown. Just make sure to use it on a regular basis, and your transmission will be fine in most cases.

Main Features:

• Doesn’t contain solvents
• Lowers transmission temperature
• Stops the ATF from foaming
• Can be added without draining the existing ATF
• Helps with the transmission slipping

2. Sea Foam TT-16 Trans Tune

If you need an effective additive that removes excess moisture, then Sea Foam TT-16 Trans Tune should be your choice. This product is not your everyday additive. It’s optimized to work together with both power-steering and hydraulic systems. Therefore, it might even help with solving some other problems in your vehicle.

For me, Sea Foam TT-16 Trans Tune is more of a remedy than a simple additive. You have absolutely nothing to lose if you give it a chance. It won’t leave any negative effects on your transmission since the viscosity of your ATF will remain the same and the seals won’t swell and break. Therefore, this additive is probably one of the safest options that you’ll be able to find out there.

Moreover, Trans Tune will reduce rough or erratic shifting and smooth out the transition between gears. It’s truly an amazing solution for all gearboxes that are in dire need of a quick fix. Unfortunately, it doesn’t support manual transmissions. Yet, you will be able to use it on a wide variety of automatic ones.

Main Features:

• Compatible with power steering and hydraulic systems
• Doesn’t alter ATF’s viscosity
• Doesn’t affect the seals
• Reduces shudder and smoothens shifting
• Removes excess moisture
• See price on Amazon

3. Hot Shot’s Secret HSSTSE32Z

If you own a diesel vehicle, you probably know how hard it is to find an appropriate transmission additive. Look no further since Hot Shot’s Secret should be your product of choice.

This additive is not intended to reduce the temperature of diesel engines per se. It is also optimized for gas engines and delivers an outstanding performance too. If you use it on a regular basis, you will almost completely prevent transmission overheating. Moreover, it also serves as a cleaning agent that removes all varnish from metal parts, including rust and corrosion!

But this product wouldn’t be so reputable without its exceptional lubricity. As soon as you pour it in your vehicle, it will reduce friction to a bare minimum and smooth out gear changes. As a result, transmission parts will last longer and become more resistant to wear.

I would truly recommend this product to all drivers who have a hard time finding the right additive for their diesel cars. It can do so much good to a transmission system for a price that is affordable, to say the least.

Main Features:

• Optimized for vehicles with diesel and gas engines
• Provides almost instant results
• Removes varnish from metal parts
• Reduces transmission temperature
• Has an exceptional lubricity

4. Dr. Tranny Instant Shudder Fix

Dr. Tranny Instant Shudder Fix is an optimal solution for all transmissions with serious shuddering issues. This product was particularly designed to get rid of the growl of old and worn torque converters.

The manufacturer states that Dr. Tranny can reduce wear four times as much as other transmission additives. It’s no wonder — its lubricity is outstanding and its main purpose is to minimize friction as much as possible.

With this product, the results will come instantly. As soon as you pour it directly into the ATF and start driving, you will see that shuddering is almost completely gone.

At first, you’ll probably be skeptical about this product and think that it’s too pricey since it comes in a 2 oz package. But you probably won’t need more than one tube in order to fix shudder. However, if the issue is persistent, I would advise you to visit your mechanic anyway.

Dr. Tranny compound is applicable only to automatic transmissions and is commonly used in Honda and Ford models. Unfortunately, it won’t work with gearboxes of Ford type F or CVT transmissions.

Main Features:

• Reduces wear four times more than competing products
• Specially designed to combat shudder
• Works in an instant
• Compatible with most automatic transmissions

5. Liqui Moly 20040 Automatic Transmission Additive

Not only will Liqui Moly 20040 fix some of your transmission issues but also improve performance of power steering system. This additive would be a perfect choice for those who wish to deal with transmission and power steering problems at the same time and save some money while doing it.

If you use it on a regular basis, Liqui Moly will reduce the wear on parts. Moreover, it will regenerate the seals, clean them, protect them, and return to pristine condition. It will also clean ducts and holes in your gearbox and improve oil performance. And as soon as you start driving, you’ll see that the shifting has become quieter and that transmission shudder is gone.

Since Liqui Moly is more of a paste than a liquid, you won’t have a problem mixing it with your existing ATF. Just keep in mind that this product is intended only for automatic transmissions.

Main Features:

• Improves power steering
• Reduces the wear on parts
• Regenerates the seals
• Cleans the gearbox
• Dampens the shifting noise

6. Prolong Super Lubricants PSL15000 Automatic & Manual Transmission Treatment

Prolong Super Lubricants PSL 15000 is optimized both for automatic and manual transmissions. Sadly, you won’t be able to use this product if you have a CVT type gearbox.

This product does an amazing job when it comes to treating all metal surfaces. It forms a protective layer that reduces the wear on them. With it, your gearbox will become more responsive, and there will be no shuddering or weird noises during shifting. Moreover, owners of cars with manual transmissions will get the most out of this product. It will smooth out gear changes in an instant and prevent future transmission jerking.

But that’s not all. Unlike some other additives, PSL 15000 works in unison with the ATF in order to reduce heat. Also, too much friction won’t be a problem anymore thanks to its outstanding lubricity. You can rest assured that this product will help your transmission maintain amazing performance even under extreme pressure.

And if you want to see what this product can really do, try to accelerate quickly. Your car will no longer hesitate when shifting even if you’re driving fast.

Finally, if the features of this additive didn’t convince you to buy it, remember all those costly transmission repairs. With Prolong Super Lubricants PSL 1500, your transmission will last longer, and you’ll have to visit the mechanic only for regular maintenance.

Main Features:

• Gives better responsiveness to automatic transmissions
• Manual transmissions will shift gears smoother than before
• Forms a protective layer to reduce wear
• Cools down the transmission and reduces friction
• Compatible with automatic and manual transmissions

The Bottom Line

Transmission fluids and additives are important because they allow you to prolong the life of your gearbox and to keep it in a pristine condition. Without them, the friction causes considerable wear on parts that can lead to serious problems.

But their main benefit is that they cool down the entire system. If the gearbox overheats, it will experience a breakdown, and then you’ll have to pay more than $1,000 in order to fix it. So, if you make sure to change your ATF on a regular basis and even mix some additives in it, you can prevent that outcome.

Unfortunately, ATFs and additives won’t be able to help you at all times. On some occasions, if the rattling doesn’t stop or if there’s still a delay between gears, you should visit a mechanic in order to find out the cause.

Finally, bear in mind that the rattle doesn’t always come from the transmission itself. So, before you act and buy an additive, make sure to check whether it’s your speakers, the door, or maybe windshield wipers that cause such weird noises.

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