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2018 Forester 2.5i CVT Sold for 2018 Toyota Tacoma. Subaru simply not for towing.
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Discussion Starter · #1 ·
Hi all, new to this forum since I purchased a North American 2018 Forester 2.5i about six months ago.

Been interested in learning about the CVT transmission and curious about the temperatures it operates at for fluid change intervals, etc.

I purchased a Vgate iCar2 OBDII reader and have been using ActiveOBD (free version) on Android phone to monitor the temperatures. This setup worked for me. Check out my uploaded images.

I have been shocked to see my CVT temperatures up to 216 degrees F in normal highway and city driving! My CVT regularly runs at about 195 degrees F and up in normal operation. I do not tow, off-road or do any aggressive driving to get these temps.

I think the "problem" lies with the CVT oil "cooling" system being a coolant-based heat exchanger. The CVT fluid runs through a heat exhanger that uses coolant to warm and cool? the CVT fluid. I think the design may be good for cold climate markets or short drives to help warm the fluid to operating temps quickly. I live in the southeast USA where ambient temps are usually 80 to 95 most of the year.

My coolant temperature normally tops out at about 198 degrees F. That means the CVT fluid is being routed through a device that heats the CVT fluid to at least 198 degrees F. I have a copy of the 2015 Subaru Field Service Manual (FSM) and thier own manual states the operating CVT temperature is between 140-176 degrees F. Most AT fluid is said to lose 50% of it's life for every 20 degrees F above 175F. So by design the Forester CVT heat exchanger is reducing the life of the fluid by at least 50% off the start.

I understand some markets for Foresters have external air based CVT coolers, not sure if this was a consideration for the issue or if North America is considered a cold climate and thats why they have coolant exchangers in them. I can imagine that since this information is not available on the dash gauges that many owners are driving around with the same problem, don't have a clue, and never change the CVT fluid under the severe use schedule.

To me this is a poor design and automatically places the customer in the position of having to do expensive "severe service" maintenance because Subaru designed the CVT to run hot.

I have an email in to Subaru for an answer and solution, it's been weeks and they have not replied stating they are waiting for the technical department to chime in. I suspect they will just tell me to change the fluid under severe service intervals (at my expense).

I am considering a tranny oil cooler after I find out if they will install one or not.

Has anyone dealt with this issue or have the same problem?
 

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2019 Crosstrek 2018 XT
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You think all of the automotive engineers allowed this "problem to continue for 70 years and hundreds of millions of auto tranny setups?
 

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2018 Forester 2.5i CVT Sold for 2018 Toyota Tacoma. Subaru simply not for towing.
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Discussion Starter · #3 ·
Its not an engineering problem when used in the appropriate climate it was engineered for. But it is an engineering problem when Subaru sells the same setup to markets that have environments where it would be detrimental. That's what I think since you asked.
 

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2014 Forester XT CVT w/ S & S#
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I have seen over 240F CVT-F temp in my XT and dont consider it a problem at all, as that has been when towing over mountain passes. Not an everyday occurrence, but something I do maybe once a month. Also, its not causing any issues as far as decreasing performance of the CVT unit in efficiency or power delivery long term.

The severe use schedule is a bit of a joke(seems almost everyone but grandma would qualify with modern driving situations), but was available when purchasing the car so you cant really claim that changing the CVT fluid is an unscheduled service item or any kind of surprise. Most vehicles call for a transmission fluid flush or change at some point, so it is not an uncommon service item either.

I will feel better having the fluid changed a few times over its life, but dont intend to own this Foz past the 10yr/100k warranty most of us just got. Its a great tranny IMO just a liability to replace at $8k

Plently of guys are towing and off-roading these transmissions with no long term issues.

Some people are having issues with the current CVT iteration on 'soccer mom' duties with zero harsh conditions..... so there is no predicting when a real problem is going to pop up from one of these, and even then its still a pretty rare issue. And the real problems aren't stranding people in the desert, its usually a slow fluid leak or bearing failure thats noticeable over time, not immediate 'grenading'.

So if you dont mod the engine or pretend your Forester is a Wrangler ie: if you dont create your own problems, your CVT will be fine

The only 'problem' I have with the CVT in my Forester is that its not a 6-speed manual, but thats a topic for another thread :grin2:
 

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2018 Forester 2.5i CVT Sold for 2018 Toyota Tacoma. Subaru simply not for towing.
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Discussion Starter · #7 ·
Thanks for the feedback. I agree and don't intend on abusing it or trying to do something with it that it's not designed to do. Just what Subaru advertises and claims it is used for, main roads, light off-road (that most cars could go on really) and light towing. At least I know now the CVT runs hot. Not sure if the other market Foresters that have the air cooled CVTs run cooler or not. If I do install one, I will have the before and after data to see how much of a difference it makes. Another person I contacted had a Youtube about installing the Hayden cooler and said it brought the CVT temps down to 170s after he put it in.
 

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At least SOA has now included the 2018 CVT models in the 10 yr/100K mile like earlier models. I just received my notice yesterday and was surprised because they claimed the deficiencies of the earlier years had been resolved. Hopefully it's not the result of new problems they've encountered in the 2018 CVT's.
 

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2018 Forester 2.5i CVT Sold for 2018 Toyota Tacoma. Subaru simply not for towing.
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Discussion Starter · #10 ·
I ended up installing a Hayden 679 cooler after the OEM heat exchanger. It has lowered the median CVT temperature by about 25 degrees. Now it's more like around 170 degrees F instead of over 200 degrees in normal driving.
 

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Casper reincarnated
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Just park it in the snow until it cools down. :N_poke: :grin2:
 

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2018 Forester 2.5i CVT Sold for 2018 Toyota Tacoma. Subaru simply not for towing.
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Discussion Starter · #12 ·
Great idea McFly, except I live in central Florida...:crazy:
 

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What an interesting topic. Thank you Wirat for sharing your thoughts on the cvt. My 2017 forester non-turbo is my first subaru and also my first cvt vehicle. I bought it used with only 16000 and have only had it for a few months. So far, so good. I was glad to hear they extended the cvt warranty to 100k mi, that gives me a little peace of mind. What do you think is it worth it to invest more maintenance into the cvt than Subaru suggests or just have a wait and see approach and hope if something does happen it will occur under warranty? I don't feel my driving would be considered "severe use" under Subarus definition. I don't tow or go off road, just normal city and highway driving. A 40min drive 5 times a week with some of stop and go traffic. I do live in Texas, so we do get 100+ temps in the summer. My plan was to do an oil analysis at 30k and another at 60k. The maintenance schedule does say to inspect at those intervals, but I imagine their definition of inspect is to just check for leaks. What do you think?
 

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2019 Crosstrek 2018 XT
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I think that adding a cooler to the cvt is a bad idea for at least two reasons.
1. The cooling system has been modified. The existing system uses engine heat to regulate the cvt during hot but also COLD periods.

2. The existing setup has been designed, tested, and proven to be reliable. I have found in my 72 years that modifying equipment will many times make the equipment less reliable.

But to each his own.

I have done auto tranny oil analysis. That is a good thought. I have not investigated the best way to grab a sample. I have an oil sample pump that goes town the dipstick tube. There is none on the cvt. Makes it a bit more difficult.
 

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2018 Forester 2.5i CVT Sold for 2018 Toyota Tacoma. Subaru simply not for towing.
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Discussion Starter · #15 · (Edited)
I'm just going to speak from my own first hand experience, not from what others here want to argue over. In your case I don't think you should do anything different other than follow the "severe use" schedule if you want piece of mind. Oil is cheaper than steel!

Like you my 2018 Forester, 2.5i (non-turbo) comes with a coolant-filled CVTF cooler (with warmer). In the Subaru Field Service manual (FSM) it indicates the oil temperature warning light goes off at 125C or 257 degrees F. I know of people who have had this happen while going over mountain passes, etc, they stopped, let the car cool down and went about their day.

One very common issue with all automatic transmissions is overheating. Especially if you do some towing. I plan to do some light towing with it which is my main reason for adding the cooler. Do some research and you will find that 175 degrees F is an optimal temperature for an automatic transmission to run at. You will also find that most transmission fluids start to degrade quickly at high temperatures.

Where I live it is 80F or above for most of the year. That means as soon as I start the car, my tranny is at 80F and within a few minutes over 100F. If you live in North Dakota, this won't be the case. So in cold climates the "warmer" part of the CVTF exchanger does its job by using the coolant to warm the CVTF as is passes through it. Then it returns to the CVT sump.

In my case I regularly would see CVT temps over 200F. Why? Because my coolant runs at 198 F all the time. So yes, the CVTF cooler will "cool" the CVTF when it gets over 200F, but how efficient is that? Eventually on long drives in hot weather the CVT temperature exceeds the coolers capacity to cool and it creeps up to 216F and above.

By adding the cooler, all I have done is extended the passive return line from the CVTF cooler to the transmission and incorporated a fin and plate cooler within the line. It does nothing to the transmission except lower the temperature by about 25 degrees F. It will slow the CVTF deterioration rate and extend the life of the transmission fluid. This is all calculated by an algorithm in the ECM/ECU based on time at a given temperature. The hotter it runs the faster it deteriorates and the sooner it should be changed.

I visited my Subaru dealership and sat down with the service manager and the senior technician before I did this. We all went over the function of the CVTF cooler, the installation of the external cooler and if it would void the warranty. They said no, so long as it is installed properly after the OEM CVTF cooler. My dealer even provided me with the hose diagram to identify the inlet and outlet hoses on the CVFT cooler. They added that I am not cracking the case or modifying the transmission at all. Subaru would have to show my adding a transmission cooler caused the transmission to fail. If anything it will prevent that.

When I showed them my data from Active OBD and the higher CVT temperatures, they said in our area the maintenance should be followed under the "severe use" schedule simply based on the hot climate. I was surprised to hear this as I don't know anyone here doing that. So I plan to change my engine oil early and the tranny fluid every 24k.

There is no dipstick on these transmissions, just a drain plug and a filler plug on the side of the case. You could open the filler plug and take a sample, but I don't think it would be worth it. If I was concerned, I would just change the fluid. There is a certain temperature and procedure to check the CVTF so unless you know how to do it, I would not try.

My dealership said they have more issues with people going to quick lube places for an oil change and they end up dumping the transmission fluid, using the wrong fluid like Dexron, or problems like that rather than what I am doing. Good luck and remember there are lots of good opinions here, but some are also based on conjecture and guesses rather than fact.
 

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Here's what I could find out about taking a fluid sample. I think a sample could be taken from the filler plug, but I believe the CVTF temp has to be between 95-113F with the engine running or fluid could spill out. Just use a small syringe with some tubing to suck some fluid out. Then replace same amount with new Subaru CVTF. I think that could work. Here's some info from the FSM.

• Always use specified CVTF. Using other fluid will cause malfunction
"CAUTION:Note that when CVTF is added up to the lower section of filler plug while the transmission is in cold
condition, overfilling of CVTF occurs, causing the oil to spill out."
1) Idle the engine to raise CVTF temperature to 35 — 45°C (95 — 113°F) on Subaru Select Monitor.
2) Operate the select lever in P → R → N → D and D → N → R → P to circulate CVTF with the engine idling.
3) Lift up the vehicle while the engine is running.
4) Remove the under cover front - transmission.
5) Remove the filler plug.
6) When there is no CVTF leakage from the transmission, add the specified fluid up to the filler plug hole lower
section.
7) Install the filler plug.
NOTE:
Use a new gasket.
 

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One very common issue with all automatic transmissions is overheating. Especially if you do some towing. I plan to do some light towing with it which is my main reason for adding the cooler. Do some research and you will find that 175 degrees F is an optimal temperature for an automatic transmission to run at. You will also find that most transmission fluids start to degrade quickly at high temperatures.
Two things to keep in mind, IMO:

1) CVT is not a traditional automatic transmission. Given the drastic differences, it might be presumptions to base what is good for a CVT off of a traditional ATX.
2) CVT fluid is not the same as traditional ATF. They are not compatible. It would take knowledge of what breaks down in ATF at 175F. Is it the base oil or the additives? There are many different additives in an ATF that serve different roles that all impact ATF life. If the CVT doesn't utilize the same weak component of ATF, then there really isn't basis for a good comparison.

You might be assuming a problem that isn't exactly present for your situation.
 

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Discussion Starter · #18 · (Edited)
y0d40n3 Your FSM information is correct. This is why I said it there is a procedure and it might not be worth it to try if you weren't familiar with it.

To take a sample though, you would not have to go through all this. You could open the plug cold, draw some out, then make sure you replace the same volume you removed with new CVT fluid. A cold CVT has less chance of fluid over flowing the plug threads if the level is a bit high.

If it were me, I would first want to know if my CVT was even getting too hot to be concerned. How much does an oil sample analysis cost? For example, it might be cheaper to buy an OBD reader and view the temps you are experiencing before you do anything. I would want to know. I only paid about $15.00 US for the Vgate iCar II on Amazon and the Active OBD app I use is free, but only works with Android.
 

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Discussion Starter · #19 ·
Two things to keep in mind, IMO:

1) CVT is not a traditional automatic transmission. Given the drastic differences, it might be presumptions to base what is good for a CVT off of a traditional ATX.
2) CVT fluid is not the same as traditional ATF. They are not compatible. It would take knowledge of what breaks down in ATF at 175F. Is it the base oil or the additives? There are many different additives in an ATF that serve different roles that all impact ATF life. If the CVT doesn't utilize the same weak component of ATF, then there really isn't basis for a good comparison.

You might be assuming a problem that isn't exactly present for your situation.
Please, opine your extensive knowledge on the differences between the CVT and other transmissions, and also the differences between CVT fluid and traditional ATF fluid... (just kidding here...calm down...:wink2:)

How about I just go by Subaru official published data? Hmmm? In the Subaru FSM there are tests performed on the CVT for problem diagnosis. One such test is a Time Lag Test. In the Time Lag Test of the FSM it states in part; "Perform the test at normal operation CVTF temperature of 60-80C (140-176F). Therefore, in Subaru's own FSM, they are publishing that 140-176F is the normal operating temperature for the CVT. I live in a hot climate where the temps would go over 200F all the time. I added the cooler which brings it back down to hey....about 170F!

I'm attaching a snap shot of my reference just to show I'm not being "presumptuous"....:grin2:
 

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Casper reincarnated
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Great idea McFly, except I live in central Florida...:crazy:
Being from "Downunder" and you not having your location listed in your Account, I just took it for granted that you lived in a snow area. :icon_redface:
 
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