Change CVT Fluid After Brief Over Temp Event?

[BHopkins]

I towed a small U-Haul cargo trailer, with the Subaru Outback, loaded with furniture to my son's new house last weekend. There are a few mountain passes on the way, On one of the passes, the AT Fluid Over Temperature light came on, just as I crested the top of the pass, and was starting the descent. I decided to continue driving, reasoning that the descent at highway speeds would cool off the CVT fluid faster than stopping and idling on the side of the highway. The warning light went back off after 2 or 3 minutes of driving, and never came back on.

I checked the Owners Manual, and it doesn't state at which temperature the warning light comes on. I change the CVT fluid 30k miles ago, using OEM Subaru CVT II fluid. I was planning on changing the fluid at 60k miles.

My question is, should I change the CVT fluid early? Or should I leave it until the next planned drain and fill in another 30k miles?

Does anyone have any experience with the Subaru CVT overtemp sensor, to where they know at what temperature it turns on? And at what temperature does it go back off?

I don't have a problem doing a CVT fluid drain and fill if needed to protect my CVT. But Subaru CVT II fluid is kind of pricey, so if it really isn't needed, I'd rather stay on the regular 60k interval.

Any educated opinions?

 

[joegreen]

I would just keep running it. I would say it’s probably more common than you think that people have the over temp light come on. I did find this on the Outback forum but I’m not sure if it’s accurate. “FWIW, I have read Subaru tech training documents that state the set point for the CVT Fluid Tempwarning light is 257 degrees F”

 

[Oro_O]

I would just keep running it. I would say it’s probably more common than you think that people have the over temp light come on. I did find this on the Outback forum but I’m not sure if it’s accurate. “FWIW, I have read Subaru tech training documents that state the set point for the CVT Fluid Tempwarning light is 257 degrees F”

This sounds about right. I had a light once and checked the vehicle specs. Temp for light, IIRC, was ~264F (GM transmission). 257F is spot on 125C so that sounds like a likely trigger point.

I would do at least a partial drain and fill, then a full one at your 60K interval. High temps cook fluid fast; the life of the fluid has been shortened. Is it good for the remaining 30k? Maybe. But if I swapped in 1/3 to 1/2 new fluid I'd feel a lot better.

 

[billt460]

I once boiled the fluid in a Buick Hydramatic so badly towing my boat, it was pouring out of the transmission. I lost about 2 quarts. I pulled over until it cooled down, (about a half hour), then took it easy until I got to a gas station. I topped it off and never had a problem after that.

I drove that car another 4 years, and then we moved out to Arizona from Chicago. It made the trip without any issues, (in mid July). After 2 more years out here we sold it. It was running fine when we did.

 

[CharBaby]

A lot(not all) of older automatic trannies were more forgiving. Older THM 3 speed trannies(especially the THM 400) could handle a bit of abuse. OH, maybe not abuse but, overheating and doing what you did...let'er cool down, add new ATF(top off or D&F) and GO ! ...

 

[FordBroncoVWJeta]

Don't know much about Subaru but Honda's CVT's are a 30K mile change under "severe conditions". I'd say if you have 30K on this run and had it overheat I'd change it this time.

 

[billt460]

A lot(not all) of older automatic trannies were more forgiving. Older THM 3 speed trannies(especially the THM 400) could handle a bit of abuse. OH, maybe not abuse but, overheating and doing what you did...let'er cool down, add new ATF(top off or D&F) and GO ! ...

Here I have to agree with you. There is no way I would compare the ruggedness of a GM Hydramatic, hooked up to a 350 V-8, to one of these belt driven CVT specials they're putting in these new cars.

 

[DirectRejection]

I would properly change the fluid now and bite the bullet on the expensive OEM fluid.

The only way you could destroy the transmission is burnt fluid.

Tell your son he owes you a tomahawk steak dinner.

 

[Pablo]

I would change it now, to a good synthetic CVT fluid. With it changed, and to synthetic, a few overtemp occurrences are not a huge worry.

Amsoil CVT

 

[BISCUT]

I've never seen the overtemp light on my 17 3.6 CVT but if it were me, I would do a fluid exchange. Dealer cost for 12 quart exchange in NY cost me $350. That is worth it to me. I would be constantly "wondering" if the fluid in there was still good. This way you'd know for certain.

I see yours is a 13 2.5....double check the fluid for that one. I believe you have it right with CVT II but make sure. Subaru has 4 proprietary CVT fluids. At times causes confusion.

 

[atikovi]

I change the CVT fluid 30k miles ago, using OEM Subaru CVT II fluid. I was planning on changing the fluid at 60k miles.

Not familiar with Subaru CVT's but because Nissan CVT's have given all CVTs a bad reputation, deserved or not, 30,000 miles would be the maximum fluid change interval I would follow even in normal service.

 

[Passport1]

That same thing happened to my Suzuki while I was driving down 95 in Florida one very hot summer night. The road is flat and I was only going ~70 so it was unexpected. The car has the infamous Nissan derived Jatco cvt so I changed out the fluid at 30K miles and replaced the OEM with Valvoline CVT fluid. Hasn't happened again. I draw out two quarts with an oil extractor every other oil change now and add two new quarts. So far so good.

 

[BHopkins]

Thanks for the suggestions. I hadn't considered a partial fluid change. But if I'm going to do it, I lean towards a full drain and fill.

I just checked with my local Subaru dealership, and they quoted me $16.69/qt for CVTF II. With the reputation that CVT's have, I've always been somewhat hesitant about using aftermarket "jack of all trades, master of none" CVT fluids, particularly since a drain and fill doesn't get all the old fluid out of the fluid cooler.

 

[BHopkins]

I would change it now, to a good synthetic CVT fluid. With it changed, and to synthetic, a few overtemp occurrences are not a huge worry.

Amsoil CVT

I believe the OEM Subaru CVTF-II fluid is a full synthetic.

Don't know much about Subaru but Honda's CVT's are a 30K mile change under "severe conditions". I'd say if you have 30K on this run and had it overheat I'd change it this time.

Subaru claims it is a "lifetime" fluid. Along with most of you, I've never bought into lifetime fluids, so I have been changing the CVT fluid at a 60k mile interval.

 

[MolaKule]

I would do at least a partial drain and fill, then a full one at your 60K interval. High temps cook fluid fast; the life of the fluid has been shortened. Is it good for the remaining 30k? Maybe. But if I swapped in 1/3 to 1/2 new fluid I'd feel a lot better.

Agree. CVT fluid can oxidize and shear within 30k miles.

 

[BHopkins]

Agree. CVT fluid can oxidize and shear within 30k miles.

MolaKule, Are there certain conditions that lead to CVT fluid oxidizing and shearing as early as 30k miles? Or does it happen under normal conditions?

 

[IndyIan]

I believe the OEM Subaru CVTF-II fluid is a full synthetic.



Subaru claims it is a "lifetime" fluid. Along with most of you, I've never bought into lifetime fluids, so I have been changing the CVT fluid at a 60k mile interval.

I think if you look in your manual the "severe duty" interval is shorter than 60k miles as well. And I would stick with the subaru stuff too, I kind of doubt anyone but subaru has done significant research on what kind of unicorn tears are best for it...

 

[miden851]

i'd change it; i'm doing it every 30K on my both Hondas, drain and fill

my CVT fluid at time of change is still amber in color

with a bit of sludge at magnetic drain plug

CVT is expensive, fluids are much cheaper

 

[Revving2Redline]

Don't know much about Subaru but Honda's CVT's are a 30K mile change under "severe conditions". I'd say if you have 30K on this run and had it overheat I'd change it this time.

Excellent observation.

 

[MolaKule]

MolaKule, Are there certain conditions that lead to CVT fluid oxidizing and shearing as early as 30k miles? Or does it happen under normal conditions?

This comes from personal experience testing CVT fluids in a 2015 Pathfinder.

I would think towing would only accelerate oxidizing and shearing of the fluid.