How to Maintain a CVT

What Car Owners Need to Know

• Fluid changes are critical with a continuously variable automatic transmission; ignore “lifetime” fluid claims and change it often (30,000-60,000 miles).
• Drain and fill is safest: Avoid pressurized flushes.
• Driving habits reduce wear: Avoid shocks to the driveline (e.g., jack-rabbit starts, hitting potholes under power).

Many of today’s cars use a CVT. Cars with CVTs include popular Nissans, Subarus and Hondas, and it’s a different type of transmission than what’s historically been used prior to the early 2000s. Their appeal is that they’re not only more efficient in transferring power, but they also tend to be lighter and cheaper to manufacture.

Their downsides are that they deliver a different driving experience than most owners are used to, and some early ones suffered durability issues compared to traditional automatic transmissions. Like a traditional transmission, maintenance is an important part of making a CVT last as long as possible.

Related: Do You Really Need to Change the Transmission Fluid?

How a CVT Works

There are a few types of CVT. A belt-drive CVT uses a metal-link belt riding between two metal pulleys. The sides of the V-shaped pulleys can be moved in and out a bit to make the belt ride lower in one pulley and higher in the other, or vice versa — or anywhere in between. This allows for variable gear ratios that can change continuously to optimize efficiency based on driving conditions, hence the name.

Metal-belt CVTs used in cars contain fluid for lubrication. Some wear from the metal-to-metal belt-and-pulley contact, resulting in fine particles, is inevitable. Furthermore, heat generated by the transmission can degrade the fluid over time, reducing its lubrication properties. The combination can cause the CVT to fail, often catastrophically.

Some hybrid vehicles have what may be referred to as a “CVT,” as well, but these are often of a completely different design that does not make use of a belt and pulleys. Instead, they use electric motors and a planetary gearset to achieve the “variable” part, and have thus sometimes been differentiated by calling them an “e-CVT.” This is the type used in the popular Toyota Prius and since adopted by many other hybrids, but they’re not what we will be referring to as a CVT here.

CVT Fluid Changes

Due to particle buildup and fluid degradation, some CVT maintenance schedules call for periodic automatic transmission fluid changes, and those recommendations should — at minimum — be diligently followed.

However, some CVTs are claimed to have “lifetime transmission fluid.” Many experts cringe at the thought (even in the case of traditional automatics), arguing that not changing the fluid increases wear, thus shortening the transmission’s “lifetime.” And some of those same CVTs’ maintenance schedules may call for fluid changes under what are classified as “severe driving conditions” (typically defined as frequent short trips, driving in very hot weather, lots of stops and starts, and towing).

If your car is said to have lifetime transmission fluid under normal driving conditions, one theory is to follow the severe driving conditions maintenance schedule in regards to the CVT even if you don’t often experience those conditions. Otherwise, some experts contend that — even under normal driving conditions — changing the fluid every 30,000-60,000 miles is a good rule of thumb even if the factory recommendation is a longer interval.

Drain-and-Fill Vs. Flush

In many cases, the recommended “fluid change” is a drain-and-fill operation that is usually less complicated than with a traditional automatic. However, unlike an engine oil change, this doesn’t get out anywhere near all of the old fluid. Much of the fluid remains in the transmission, mostly in the large, doughnut-shaped torque converter. In fact, only about a third to half of the fluid typically drains out. Because of that, some people do it multiple times in fairly short succession, each time usually resulting in a greater percentage of new fluid being in the transmission.

Some shops may recommend a “flush” instead, which is supposed to get out all of the old fluid. As beneficial as that sounds, though, many experts warn against flushing the transmission fluid in either regular automatics or CVTs. That’s because some flushing techniques involve forcing pressurized fluid through the system that can dislodge particles that then collect at and clog small orifices, and it can also result in damaging seals that aren’t made to withstand that kind of pressure.

Dealership Vs. Do-It-Yourself

Although a drain-and-fill may take only about 4 quarts of transmission fluid and the procedure only half an hour, a dealership may charge a disproportionate amount for it — sobering if you’re going to have it done more than once in order to get more “new” fluid in the transmission.

However, it’s often something a traditional do-it-yourselfer can perform at home with little more than basic tools along with ramps or a jack and stands to raise the car off the ground.

CVT fluid typically costs more than traditional automatic transmission fluid — often $20 or so per quart — and it’s very important to get the proper type, which should be listed in your owners manual. It’s probably safest to buy it from the dealer (partly because the proper type for your car should be known), though you might be able to find factory fluid sold online for less.

Tips for DIYers:

• Locate and remove the fill plug before draining the fluid. CVTs often have a drain plug at the bottom of the transmission and a fill plug at the top. You want to make sure you don’t drain the fluid and then aren’t able to get the fill plug out to refill the transmission.
• There may not be a dipstick to check the fluid level. The fill plug may not include any kind of dipstick, and — as with a traditional automatic — the fluid level is important. Furthermore, on many maintenance schedules, there may be a line item to check the CVT fluid.
• To fill a CVT to the correct level, save the old fluid in whatever pan you drained it into. Pour that into (ideally) an empty 5-quart oil container (which has handy ounce markings on the side) or another measuring vessel to determine how much you drained out, then pour the same amount of new fluid back in.

Tips to Fend Off Damage

In general, CVTs don’t like shocks to the driveline, which can cause the belt to slip and create wear. Thus, it’s best to do the following:

• Avoid jack-rabbit starts.
• Try not to hit potholes or railroad tracks while under power (in other words, try to let off on the gas). When the tires “hop” and lose contact with the road, they can spin and then stop suddenly when they grip the road again.
• Avoid rapid shifting from Reverse to Drive when stuck in snow.

While CVTs can improve fuel economy and acceleration, some have proven to be less durable than traditional automatics. But careful driving and more frequent fluid changes can help extend the life of a CVT, making them fulfill their promise of better efficiency over a longer period of time.

More Service and Maintenance Advice from Cars.com:

• Spring Car Maintenance: Here’s What You Should Be Checking
• Which Car Maintenance Can You Do Yourself?
• When Should the Oxygen Sensor Be Replaced?
• What’s Included in a Tuneup?
• What Happens When You Overfill Your Car With Oil?
• What Happens When You Skip Oil Changes?

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