[Micron]

Someone once posted an excellent explanation in here about the ratio of new/old fluid after every drain/fill if you attempt to get all, or most of it changed in one service. Tried, but was not ever able to find it again. Basically, 1st time if you drain 6 out of 12 and refill, you have a 50/50 mix. Try that again, and you drain half of the old fluid but you also will drain half of what you just put in. IMO, the only way you'll get most of it in one drain/fill is to pull the trans and drain the converter, unless you can rig up a running flush. Even then, I doubt you will flush out all old fluid with 12 quarts even if you can do that. Not the way fluid moves around.

 

[Micron]

@SilverOnyx , not disagreeing that replacing all cvt fluid in an OB is not a thing, but it seems like you're saying cvt fluid doesn't get contaminated and that I'll disagree with. Gears, clutch packs, chains/pulleys all produce some degree of metal or fiber particulate just by virtue of the fact that they are in contact with each other, and boundary lubrication isn't always enough to prevent 100% of that. One difference between a modern cvt and a conventional automatic trans would be that the number of parts that work through friction are greatly diminished in the cvt, so yeah, the rate of contamination would be much less in the cvt, but there will still be some. As you rightly pointed out, towing makes fluid change a bigger concern, but I think that heat plays a bigger part in fluid degradation there.