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Buying guide for Best automatic transmission fluids

Automatic transmission fluid is one of the most important liquids in your vehicle. Without it, things come to a grinding halt – literally. You can prevent expensive transmission problems by changing your fluid regularly, following your vehicle maker’s instructions.

The challenge comes in knowing which of the dozens of products available is the right one for the job. How do you find the best automatic transmission fluid for your vehicle?

At BestReviews, we answer all your purchasing questions with our thoroughly researched recommendations and information-filled shopping guides. For everything you need to know about automatic transmission fluids before your next change is due, just keep reading.

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Why is automatic transmission fluid dyed red, pink, or green? Two reasons. One, to make it easier to spot a leak. Two, so it isn’t confused with engine oil.

What is automatic transmission fluid?

Automatic transmission fluid (ATF) needs to do two basic jobs: lubricate bearing surfaces and dissipate heat in vehicles with automatic transmissions. To do these things, automatic transmission fluid needs precise viscosity to suit the transmission concerned. It also needs to be durable – it can’t break down when it gets hot or under extreme pressure.

Different automatic transmissions have different demands. The way cars are built and the materials used have changed a lot in the last 50 years. Manufacturers use a variety of approaches, and many American cars can’t use the same automatic transmission fluids as vehicles from Europe or Asia.

There’s one golden rule with automatic transmission fluid: always buy the grade that the maker of your vehicle recommends. Not doing so can be disastrous. Unfortunately, names, codes, and packaging can be confusing.

Types of automatic transmission fluids

There are two basic types of automatic transmission fluids. Traditional (or regular) automatic transmission fluids are made from natural oils that are combined with antioxidants and corrosion inhibitors. Synthetic automatic transmission fluids are man-made chemical polymers that perform the same functions.

Synthetic ATFs are more durable and resistant to the damaging effects of heat in modern transmissions. As almost all synthetic ATFs are compatible with traditional ATFs (you can mix the two together so long as the synthetic ATF is the same grade), synthetic ATFs are beginning to dominate. However, there are a large number of older vehicles still on the road, and there are specific fluids to suit them.

Traditional ATFs

Type A and Type F are traditional ATFs that haven’t been used in new cars since the 1970s. However, there’s a thriving classic and collectors market out there, so you shouldn’t have any trouble finding appropriate grades of these automatic transmission fluids.

Dexron and Mercon are arguably the most common traditional ATFs. Both are very similar and are used in American and imported vehicles. The big step forward over Types A and F is the addition of friction modifiers – molecules that coat surfaces, thus reducing friction and heat buildup. Dexron and Mercon are the basis for many other ATFs sold under different names.

Synthetic ATFs

Highly Friction Modified (HFM) Fluids are synthetics. They are often, though not exclusively, used in European high-performance vehicles. Popular products ATF+ and 7670 are both HFMs.

Synthetic ATFs closely resemble the properties of Dexron and Mercon. Indeed, there’s a lot of confusion around Mercon V. The name suggests it’s a traditional ATF, but actually it’s synthetic. This underlines how you must be absolutely sure you get the right grade of automatic transmission fluid for your vehicle.

"Don’t worry if you drive a classic car or are thinking of investing in one. Type A and Type F automatic transmission fluids are still widely available."

Choosing an automatic transmission fluid

While you can mix and match traditional and synthetic ATFs of the same type, you absolutely cannot swap grades.

There are 20 or more variations on the four main types of automatic transmission fluids. Some are specific to a particular automaker – Nissan Matic D, K, J, and S, for example. Some are names used by aftermarket brands – Multi-Vehicle ATF, for example. So how do you choose?

For cars manufactured pre-2006 – and particularly classics – you’ll likely have limited choice. For cars manufactured post-2006, you can usually choose from traditional or synthetic automatic transmission fluids. You can buy the vehicle manufacturer’s recommended brand from a local dealer (usually the more expensive option), or you can by an aftermarket brand online or from a local auto parts dealer.

We can’t make specific recommendations because there are simply too many car models to cover. But for absolute security, you can’t go wrong with the manufacturer’s recommended brand. Whether you choose traditional or synthetic automatic transmission fluid is up to you. The former is often a little cheaper, while the latter has greater resistance to the effects of heat and friction. For example, synthetic ATF is very popular with those who frequently tow a trailer, which puts additional strain on your vehicle’s transmission.

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Did you know?
A CVT (constantly variable transmission, also called a “stepless transmission”) is not the same as an automatic transmission. As a result, they require different transmission fluids.

Prices for automatic transmission fluids

Automatic transmission fluids generally come in quart or gallon bottles. Quite often quarts will come in a pack of six. Neither size is necessarily cheaper, but a quart bottle is easier to handle if you’re just topping up.

For both traditional and synthetic automatic transmission fluids, you’ll pay somewhere between $20 and $30 a gallon.

Rebuilding a transmission costs thousands of dollars. Buy the automatic transmission fluid your vehicle needs. It’s a small investment that delivers long-term reliability.


  • If you’re buying a used vehicle, ask when the automatic transmission fluid was last changed. Be cautious. It’s not uncommon for an unscrupulous seller to put heavy-duty oil in a transmission to disguise problems. Check the color of the automatic transmission fluid using a white rag so you can see it clearly. It should be pink, red, or green (brands vary). If it’s black or brown, it needs changing. If it looks like fresh motor oil, walk away!

  • Check your automatic transmission fluid levels regularly. A minor leak can quickly turn into a major mechanical disaster. With automatic transmissions, you’ll often have a dipstick under the hood to make this easy. Be sure you know which is for the transmission and which is for the crankcase (engine oil). Usually checking is done with the motor running, but have a look in your owner’s manual to make sure.

  • Whines, rumbles, struggling to shift gears, or popping out of gear are sure signs of transmission problems. Every mile you drive will only make things worse. If you experience these problems, your transmission needs to be checked immediately.

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There are many types of automatic transmission fluids. It’s vital to get the right grade for your vehicle. The details are in your owner’s manual.


Q. Why do I need to change my automatic transmission fluid?

A. Automatic transmissions run relatively hot compared to manual drivetrains, and that heat eventually breaks down the chemical composition of the fluid. When that happens, it neither cools nor lubricates as well as it should, which accelerates wear.

That’s not all. Even the best maintained transmission wears eventually. Tiny metal particles then contaminate the fluid, which is why it turns a darker color. If these particles aren't removed at the suggested service intervals, they will reduce transmission life and could cause a breakdown.

Q. How often should I change my automatic transmission fluid?

A. It varies from one vehicle to the next, so it’s absolutely vital to check the manufacturer’s recommendations. You’ll find them in your owner’s manual (or online if you don’t have it). Some older vehicles may need fluid changes as frequently as every 30,000 miles, though modern automatic transmissions will run 60,000 to 100,000 miles or more before they need a fluid change.

A new generation of “lifetime fluids” have been designed that never need changing. These synthetic automatic transmission fluids are expected to last the entire life of the vehicle, so eventually transmission fluid changes may become a thing of the past. Currently, these ATFs are not common, however, and are only installed in new vehicles.

Q. Is it difficult to change my automatic transmission fluid?

A. It’s not a complex operation – and there are a number of videos online that can help – but it does require patience, and it’s certainly messy.

The biggest challenge is that most automatic transmissions don’t have a drain plug, so the whole pan has to come off to remove the old fluid. It’s a job that has to be done anyway because there’s a filter in there you’ll want to change. You’ll also need a new gasket.

It’s a time-consuming task, rather than a difficult one, and doing it yourself will save you a healthy chunk of change. But if you have any doubts, you should take your vehicle to a qualified mechanic for an automatic transmission fluid change.

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