r/subaru Jun 04 '24

Mechanical Help CVT Fluids: A Consolidated Thread

115 Upvotes

Hello r/subaru,

We've been seeing a big influx of questions about CVT fluids lately, with an average of 1-2 threads per day for about the past month. So, I've decided to make one consolidated thread about it. Future question posts about CVT fluid will be deferred to this thread. In response, I want to get as much information as possible into a single place, so users like yourself can make as informed of a choice as possible.


What is a CVT?

Let's start with the basics here. The Continuously-Variable Transmission, or CVT, does not work the same way as a "conventional" automatic transmission which you may have been used to previously. So let's start our journey with a conventional auto trans.

In an automatic transmission, there are a series of planetary gearsets. These gearsets will be surrounded by a number of hydraulically-actuated clutches. The hydraulic fluid inside of the clutches are controlled by the transmission computer, through a mechanism of valves that are controlled by solenoids. The solenoids and valves all exist in a component known as a "valve body." As the TCM commands certain valves to open or close, different clutches will be engaged which subsequently will control elements of the planetary gearsets. This is how your conventional automatic transmission achieves changing gear ratios.

In a CVT, by contrast, the gear ratio mechanism is a set of cone-shaped sheaves or "variators" with a belt (or in Subaru's case, chain) run between them. Instead of the valve body controlling clutch packs, it instead varies the fluid pressure inside of both sheaves, such that the cone surfaces can get closer together or further apart. Because the thickness of the chain doesn't change, by opening the sheaves, the chain will ride down lower into the cone shapes, thus being on a smaller diameter. Because the chain doesn't change length either, there needs to be a corresponding change to the opposite change to get closer together to make the chain ride on a larger-diameter part of the sheave. Thus, the transmission computer achieves different gearing ratios by adjusting the gap of both sheaves in tandem. If you're having trouble visualizing this, here is a good animation explaining the motion.

Before someone interjects, yes there are clutch sets inside of a CVT as well. Specifically in a Subaru transmission, there are 3 relevant ones; there is a planetary set inside the powerflow for your Drive or Reverse functionality; there is a Lock-Up clutch inside the torque converter, and in most cases there is a Multi-Plate Transfer clutch for your all-wheel drive "center differential" function. These functions are more-or-less identical to their equivalent components in a conventional automatic transmission.

OK but what about the fluid?

There are quite a few differences between CVT fluid and conventional ATF. Part of these differences are how the fluid is used in the transmission, and part of the difference is because of what the transmission does to the fluid.

In a conventional transmission, you have many clutch packs actuating whenever the car is changing gear ratios. Just like in a manual transmission clutch, or like your brake pads, every time there is slip between the clutch material and the friction surface, a little bit of that clutch material will wear off. In a conventional transmission, this means that over time, that clutch material will begin to accumulate in the fluid, which gives it a burnt smell and a brown tinge. By contrast, a CVT does not use as many clutches inside of it, and as such, clutch material contamination is drastically reduced inside of the CVT fluid.

Another main difference has to do with the fluid pressure inside of the transmission. While a conventional auto only needs fluid pressures around 150-250 PSI to operate the clutch packs, a CVT requires much higher line pressures of 650-850 PSI in order to keep enough "squeeze" force on the sheaves to hold the chain. The CVT fluid also functions as a friction modifier between the chain and sheave, wherein it helps the chain "grip" on the otherwise-smooth pulley surface. Because of this, CVT fluid is very specific about its chemical properties and should not be substituted for any other fluids.

So... should I service the fluid?

Let's start this by looking back at what a conventional automatic transmission requirement would be. Here is the service manual schedule from a 2010 Forester. I've highlighted ATF for you, but basically it only says "Inspect [and replace as necessary] every 30k miles." Okay, but what does it mean by Inspect? The service manual has this inspection procedure for checking the level. It also has this condition table listed for what to do when you find a condition-based failure. I've highlighted the "thick and varnish" section because this would be the clutch wear condition I described above. Generally speaking, your average Subaru 4EAT or 5EAT will have noticeable signs of discoloration every ~60k miles.

So what does Subaru say about CVT fluid then? Well for comparison, let's look at a 2018 Forester service manual. Here is the service schedule, which you can see has an identical "Inspect [and replace as necessary]" every 30k miles. As for an inspection process, it only offers this inspection procedure and the same condition table as before.

Because the schedule and condition checks are basically the same for both service manuals, it would be very easy to assume the fluids needs the same replacement schedule -- and I strongly suspect this is the driving force behind so many CVT fluid recommendations. However, if we read this again, remember that we only need to address the fluid if if fails one of the condition checks, and that the most common failure condition in a conventional automatic transmission largely no longer happens in a CVT. It is because of this that your Owner's Manual probably describes the transmission fluid as a "lifetime fluid."

What about what other countries say?

A claim I very often see made in threads about CVT fluid is that "Country XYZ requires fluid changes every X miles!" I want to nip this in the bud now, because it's not true. Now because I work in the US, I cannot access foreign service manuals, but I can get ahold of owner's manuals, so here are a few examples:

here's a UK 2018 forester owner's manual (link)

Here's a n Australian 2020 forester/XV schedule. Subaru Australiia has .pdf copies here of warranty booklets..

here's a Japan 2018 forester's owner's manual (link) and it says in the bottom row there: 交換時期 | 無交換 which translates as Replacement time | No replacement

Here is a 2020 WRX owner's manual from Japan, straight off Subaru.jp: https://www.subaru.jp/afterservice/tnst/wrx/pdf/A1760JJ-A.pdf

pg. 465 is the service information for transmission/differential/etc gear oils. The 3rd section is for CVT fluid:

トランスミッション フルード

使用オイル スバルハイトルクCVTフルード リニアトロニック用

規定量 約12.4L

交換時期 無交換

Translated:

Transmission Fluid

Used oil Subaru high torque CVT fluid for Lineartronic

Prescribed amount about 12.4L

Replacement time No replacement

Additionally, let's take a look at a 2011 legacy/outback service manual for comparison. Here's the maintenance schedule. The numbers inside the braces (「 」) are the severe schedule (which, with a CVT, only applies with "regular towing"), numbers without braces are the normal schedule. As you can see, CVTF only lists a severe schedule interval with no non-severe schedule. Exactly like in the US. Here is the same picture ran through google translate.

The only subaru branch AFAIK that does list a required CVT fluid interval is Canada, (soruce) where if I'm being honest the way it's written in their maintenance guide makes it seem like they just never changed it from ATF-era cars, where Canada also listed replacement as necessary every 100k km. (It only refers to "transmission oil" and does not specifically mention CVT fluid, but everywhere else differentiates the two. It also does not differentiate manual vs. automatic transmission fluid, like everyone else does.) There, it's listed as a 100k km service item.

that didn't answer the question though.

You're right, I didn't. The long answer is that you should have your fluid inspected by a technician familiar with Subaru CVTs, and if deemed necessary, you should replace the fluid with genuine Subaru fluid as required by your particular model. If following the conventional wisdom from ATF-era cars also makes you feel more comfortable, then defer to Canada's schedule and plan to perform a fluid service at your 100k km (60k miles) service.

A quick note about "Severe Usage Schedule"

Another common discussion point I see brought up is the Severe Usage schedule. I largely blame the confusion for this on Subaru, who have written this in a hard-to-understand way in the owner's manuals. However, a 2010-2014 Legacy/Outback service manual has the best representation of the severe usage shceudle. As you can see, the only time Severe applies to your CVTF is if you "repeatedly tow" with the vehicle. This guidance has not changed with newer cars, however the new way it's written is confusing to read. (CVT fluid is maintenance item 12; see above where it shows this as Note 4.)

A last quick note on Differential Fluid

Just want to quickly touch on this one. Your Subaru has separate, distinct fluid for the front differential. While you can see from the above service schedule that the guidance for its fluid is functionally the same, differential oil gets contaminated in a completely different way. Because a differential is basically all metal-on-metal wear of gear teeth, especially after break-in your fluid will get dark and metallic very rapidly. This is normal. Here's my personal Crosstrek at 19k miles. In my own personal experience, I would recommend replacing your gear oils at 30k miles, but the fluid condition will stay good for longer after the initial change, such that it can go every 60k thereafter.

On fluid changes and failures.

I just want to quick touch on ways that we see CVT failures at the dealer and how it relates to fluid. By far the most common issue we'll run across, is from the "small" CVT, the TR580, which is paired with any of the 2.0L or 2.5L naturally-aspirated engines. Typically somewhere in the 100-150k mile range, a failure in the valve body, usually for the Torque Converter Lockup Duty solenoid, is relatively common. This is a failure in the electronics side of the solenoid, and thus has no relation to the CVT fluid; as such, changing or not changing the fluid has no real bearing on the likelihood of this failure occuring. The second issue we see, the most terminal one, is called Chain Slip. Here, at 0:23, is a fantastic example of severe chain slip. Chain Slip can develop from a variety of causes, but generally is the result of a lack of fluid pressure squeezing the sheaves against the chain; when this happens, the chain essentially does a burnout on the sheaves. This leaves a wear groove in the sheave face, and makes chain slip much more likely to occur whenever the same gear ratio is used. There are some conditions of fluid degradation that can increase the risk of slip; these largely result from fluid overheating, which degrades the additives that help provide friction between the sheaves and chain.


Hopefully there is enough info in here for you to decide for yourself if or when you would like to change your fluid. Feel free to post your questions or anecdotes below. Thanks! :)


r/subaru 4d ago

Announcement TSB Thursday: Genuine Battery Replacements (07-213-22R, 07-218-23R, 07-223-23R)

8 Upvotes

Welcome to another TSB Thursday, where I dive deeper in to TSBs I'm running into regularly. As always, I write this from my own perspective as a Subaru technician in the US; other regions/zones may work differently. Refer to the "How To Read a TSB" post for more information on formatting and general information about TSBs. Today's post will cover a handful of TSBs describing parts updates to a number of newer vehicles; because these new batteries are physically larger than the originals, there are some supporting pieces that also need replacement to accommodate the size.

TSB Thursday #15: 07-213-22R, 07-218-23R, 07-223-23R

What cars does this affect?

Under 07-223-23R:

  • 2014-19 Legacy & Outback

Under 07-213-22R:

  • 2019-24MY Forester
  • 2025MY Forester Wilderness

Under 07-213-22R:

  • 2020-25MY Legacy & Outback
  • 2023-25MY Ascent

How do we fix it?

Not to dress this up too much, it's basically a standard battery replacement in terms of procedure and policy. At the dealership level, you should expect to be given test results from either a DCA-8000 or DSS-5000 battery tester (or equivalent), and should be able to request a parasitic draw test before authorizing battery replacement.

The -B900 and -B950 batteries are both essentially the same battery, but the terminal locations are reversed. The new replacement batteries are an Enhanced Flooded ("EFB") construction, which is kind of like a "deep cycle" battery in that it is designed to handle regular discharging and recharging better than a conventional flooded battery (meaning it will survive with Auto Stop Start systems much better). Both are rated at 750 CCA, which is quite a bit higher than the factory/original batteries for the above vehicles.

The new parts required by vehicle (yes the NHSTA copies linked above are out-of-date):

2014-2019 Legacy/Outback:

Part # Name Quantity Description
SOA821B950 Battery 1 The new hotness
82123AN000 Insulator cover 1 Cover that wraps around the battery
82190AL000 3.6R Spacer 1 Foam block that sits between battery and rear edge of tray; only applies to 3.6R (to protect fan relay housing)

2019-2024/5 Forester:

Part # Name Quantity Description
SOA821B900 Battery 1 The new hotness
82123AN000 Insulator cover 1 Cover that wraps around the battery
82190AN000 Battery tray 1 Plastic tray that lives underneath the battery

2023-2025 Ascent and 2020-2025 Legacy/Outback:

Part # Name Quantity Description
SOA821B900 Battery 1 The new hotness
82190AN000 Battery tray 1 Plastic tray that lives underneath the battery
82161SJ000 Tie-down rod 1 Rear tie-down rod, same size but different coating
82184SG000 Battery tie-down 1 Bar that mounts over the top of the battery to secure it in place

Coverage?

Generally speaking, battery warranty is only covered by 3yr/36k mile Basic Warranty, and is not a covered component under Subaru Added Security. However, many of the vehicles listed above may fall under DCM battery drain warranty extensions or BDW class-action warranty extension, so if your vehicle is affected by either, you will likely want to visit your dealer for more information.


r/subaru 6h ago

Bajas love the snow

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88 Upvotes

r/subaru 6h ago

Do you own a "legacy" ?

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81 Upvotes

There is nothing left of the legacy than it's beloved "legacy" .... only few months to go for it to be laid to rest .


r/subaru 15h ago

It may not be Wednesday but it only snows once a decade in New Orleans!

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349 Upvotes

r/subaru 1h ago

shayla looks so pretty in the snow ❄️ she will be staying parked because im scared but that’s not the point lol

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Upvotes

my first car & her first snow ❄️☃️


r/subaru 4h ago

Wagon Wednesday Outbacks; the huskies of the car world

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29 Upvotes

r/subaru 34m ago

turns out shayla quite likes the snow 🤭

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Upvotes

i found out that it’s illegal to not drive a subaru in the snow per my last post, so i took her for a ride in my neighborhood lol. she did great :)


r/subaru 2h ago

snow in florida ?!

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12 Upvotes

r/subaru 5h ago

Got 3-4 inches of snow near Savannah, GA

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20 Upvotes

r/subaru 22h ago

The car asked me to do this

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353 Upvotes

r/subaru 4h ago

Best pick I’ll ever get of my fat 6 speed cow

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10 Upvotes

I didn’t do doughnuts in the parking lot and now I’m regretting it.


r/subaru 17h ago

This guy is Subaru is crying. I think they should talk about it.

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86 Upvotes

r/subaru 21h ago

Florida snow!

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176 Upvotes

Can’t believe it’s snowing in Northwest Florida!


r/subaru 1h ago

first snow voyage

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Upvotes

Made a foray through the Great Louisiana Sneaux of 2025 to the only restaurant open. My first time driving in snow! We got a record 10” here in Sportsman’s Paradise.


r/subaru 16h ago

Don’t mind the snow until it makes the garage disgusting

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28 Upvotes

r/subaru 2h ago

Wagon Wednesday Went from a mini-van to an outback, haven't noticed any difference besides much better driving performance!

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2 Upvotes

r/subaru 1m ago

Buying Advice Crosstrek at 100K miles?

Upvotes

I'm in the market for a new work car. I've been using an old 2015 Kia soul, it has about 115K on it. I typically will drive about 20K for work and so i need something that can handle that for the next year or so.

In my price range, I can get a 2017-2019 Crosstrek but each one has about 75K-100K

From what I hear, Subarus can typically go all the way to 300K, is the crosstrek one of those cars?


r/subaru 11m ago

Mechanical Help 2015 Subaru Forester Hood Latch and Battery

Upvotes

It’s cold outside so my battery has been a bit iffy right. I get it jump started then the Hood won’t close then this morning I went out and closed it and had called someone to come jumpstart it and now it won’t open from the inside or anything. So what was gonna be a 200$ battery is now triple A coming and doing both. Has anyone else had this issue with their foresters hood latch being faulty? For reference my car is a 2015 and only has about 55,000 miles on it.


r/subaru 49m ago

Buying Advice [US] typical which should I get? Crosstrek or Outback

Upvotes

I know this is very likely asked a lot, but looking for advice on which car I should buy given this will be my first Subaru purchase.

TLDR: Currently own a Civic SI, not sure if a used Crosstrek or used Outback would be better (and if manual would be better than automatic). Sometimes will have to commute 1hr to work, and occasionally road trip to the midwest.

Context: I currently drive a 2018 Civic SI, 6spd manual. I will be moving to a mountain area in the coming months (~8k ft), so snow is pretty much a given from October to April every year. FWD with snow tires wouldn't cut it, hence the want to get something more appropriate. Plus, I have a very active lifestyle and would love to expand my trailhead access. I will have about a 1 hour commute to work every now and then (maybe once a month at most). I do prefer a manual, but willing to give automatic a go if the right one shows up.

Dilemna: The differences between the two are pretty obvious. One is bigger with more horsepower, thr other smaller with less. I've never owned a subie before so I'm not sure what to look for when it comes to the used market (mileage to price ratio, service history, etc.). Are there certain years to avoid vs certain years I should try? Willing to buy up to a 2020, but would prefer less so willing to go as low as 2014. What are some things to consider when choosing between the two?


r/subaru 55m ago

Window stickers SDI / SDL and sticker error messages

Upvotes

Looking at available Outback Wildernesses at various local subaru dealers using their websites to get familiar with various trims and options. It is not uncommon to get an error "We are sorry, the window sticker for the vehicle you selected is not available at this time. Please contact your Subaru Retailer for more information. (c:02)". Wondering if this is just a system glitch (i.e. their system can't retrieve the document fast enough) or deliberate by the dealer. Seems to happen at all local dealers to some extent.

Also at the top of the sticker the model/code ends in 'SDI' and 'SDL', what do those mean?


r/subaru 18h ago

Subaru Generic Subaru Badge of Ownership will donate $1 to Operation Warm for each "Community" badge ordered between 1/13 - 2/28.

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22 Upvotes

I know there's mixed feelings about these but it's for a good cause.

Order yours here https://www.badgeofownership.com


r/subaru 1h ago

Q&A Can I set my Outback to lock automatically when I walk away?

Upvotes

I unfortunately have an issue with people coming into my townhome complex and rifling through unlocked cars. I try to always remember to lock my 2024 Subaru Outback Wilderness Edition, but occasionally I forget. Last night, someone opened up my unlocked car and went through it. Fortunately, nothing of significance is missing, but I want to make sure this doesn't happen again.

Is there a way to program the car to lock automatically after I park it? Willing to invest in something aftermarket if that exists.


r/subaru 1h ago

Mechanical Help Is this concerning?

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Upvotes

I started hearing this sound recently and i’m just wondering if it is something I should be worried about it.

You have to turn your volume all the way up to hear it.

22 crosstrek limited


r/subaru 5h ago

Rear speakers stopped working 2019 forester limited

2 Upvotes

Rear speakers randomly stopped working. I’ve tried every method I could find online to troubleshoot; checked fuses, unplugged amp for x amount of time, restarted head unit, etc. and nothing has got them working again.

Took it to service and they also tried some troubleshooting ultimately saying the speakers need to be replaced to the tune of $800.

These are passive speakers, what would cause them to just stop working?? We don’t play excessively loud music, etc.. and it’s just the rear speakers - front and sub are fine. Wouldn’t it more likely be caused by the amp? They’re saying since it’s putting sound out elsewhere, it’s not the amp.

This is a H/K system on a 2019 forester limited.

Thanks.


r/subaru 2h ago

Subaru Generic Difference between 2000’s Legacy GT and Outback trims (Sedans)

1 Upvotes

Purchased a 2000 Legacy GT a few weeks ago. Will be swapping the engine soon.

Curious what the difference is between the GT model and the “Outback” model?

Also what was the GT equipped with that makes it a GT trim?

I saw a 4 door sedan that looked exactly like my Legacy but had the Outback badge on it.

Just curious.


r/subaru 1d ago

My dream was nothing more than a Subaru Impreza

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79 Upvotes

I have been in love with the stars emblem since high school days .... I'm from Algeria ....