There's something I don't understand about the transmission fluid drain and fill process on a 2015 Subaru

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Oct 25, 2014
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2015 Subaru Crosstrek CVT

I'm going to drain the fluid from the pan and then add approximately 4 quartz of fluid until it reaches the fill hole. Once the transmission temp gets between 95 and 113F, I'm going to shift from Park to Drive and then back to Park, and then add approximately 1.5 quarts until the fluid comes out of the fill hole.

When I add the new fluid it's going to get mixed with the fluid that has expanded due to the raised temperature. Once that new fluid expands, the level will rise well over the fill hole, which will make it overfilled. The fluid can't drain out by the time it expands because there will be a filler plug in place.

Now let's say I loosened the fill plug the very next day while the transmission fluid temp was between 95 and 113F. Fluid would most certainly leak from the filler hole because the 1.5 quarts that was added had not yet expanded during the drain and fill process.

The service manual for "Adjustment" says that the correct amount of fluid should be at the lower level of the filler plug when checked between 95 and 113F.

What gives? The "Drain and Fill" process and the "Adjustment" process would cause different amounts of fluid in the transmission.

Am I making any sense in my thinking?
 
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Just measure what comes out. Sometimes not even half comes out.

Add the same amount that came out and you can also double check using the fill hole procedure just in case you were short to begin with.
 
The trans holds 13 qt. Adding 1.5 qt of room temp (70f) fluid to 11.5 qt of 95-100f fluid will not cause a drastic change in temperature. The fluid will mix almost instantly.
 


should answer your question. He leaves the fill hole open until its a steady thin stream. His goal was to replace most of the fluid so he goes a step further but if you don't want to do that, you just leave the fill hole open until the temp reaches 100-110F and then seal it.

Max Weber also has a video to perform a flush but its more complicated that MT's.
 
Just be aware that Subaru now uses four different CVT fluids, and none is compatible with the others, so use the right one. They are Subaru CVTFII, Subaru High Torque CVTF, CVTF III, and CVTF LV. The last two fluids are new for the 2020 model year. I would stick with Subaru CVTF products only there have been issues with even using the wrong Subaru fluid never mind some other maker’s.
 
Just be aware that Subaru now uses four different CVT fluids, and none is compatible with the others, so use the right one. They are Subaru CVTFII, Subaru High Torque CVTF, CVTF III, and CVTF LV. The last two fluids are new for the 2020 model year. I would stick with Subaru CVTF products only there have been issues with even using the wrong Subaru fluid never mind some other maker’s.
Yeah, I bought 6 quarts of the CVTF-II. It seems most people are using 5.5. The dealer is close enough in case I need another quart.
 
Yeah, I bought 6 quarts of the CVTF-II. It seems most people are using 5.5. The dealer is close enough in case I need another quart.

5.75 for me.
 

5.75 for me.
Hey Critic,

Thanks for detailing your work here! If I understand correctly, once you started the car after the initial 4 quarts fill, you immediately added the additional 2 quarts and started cycling the select lever until you hit 95F? Subaru Manual states to idle the engine to raise the CVTF temp to 95-113F, then cycle the lever to circulate the CVTF and then adjust the CVTF (add the remaining 1.5 quarts) level.

Question: Does it make any difference whether the cycling and top-off occur prior to or after the target temperature?

Thanks again for the write-up.
 
Hey Critic,

Thanks for detailing your work here! If I understand correctly, once you started the car after the initial 4 quarts fill, you immediately added the additional 2 quarts and started cycling the select lever until you hit 95F? Subaru Manual states to idle the engine to raise the CVTF temp to 95-113F, then cycle the lever to circulate the CVTF and then adjust the CVTF (add the remaining 1.5 quarts) level.

Question: Does it make any difference whether the cycling and top-off occur prior to or after the target temperature?

Thanks again for the write-up.
I doubt it makes a difference. I try not to operate the transmission when it is low on fluid, so I top off to approximately the correct level before moving the shift lever.
 
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