I have a 2021 forester sport with cvt I bought new. no issues. 23k miles. subaru of usa says transmission SEALED FOR LIFE, dont change fluid. but in japan subaru has owners change the fluid. fluid is not cheap and takes quite a bit of it but a cvt replacement is like $8k. what do you recommend?
Change the fluid regularly if you want the longest life out of that thing.
Your question is explained in our FAQ.
Manufacturers want their cars to appear as low maintenance as possible because they sell more that way. The "life" they refer to, is the powertrain warranty period. So if you want the transmission to last beyond that, change the fluid. Often. CVTs are weak.
No transmission is "sealed for life." The "lifetime" of the transmission is the manufacturer's warranty period, 5 years or 60k miles, whichever comes first. As soon as you roll it over 60k or 5 years, it's on you if the tranny goes out, not the manufacturer. They've skimped on transmission dipsticks so save a few bucks and they hide behind "lifetime" fluid because most members of the general public believe what the manufacturers say. "Lifetime" fluid is hogwash, and just contributes to planned obsolencence.
Every 30k miles you should probably change your fluid. CVTs require more frequent transmission fluid changes because they run dirtier than a conventional automatic. Conventional automatics are hydraulic based, CVTs operate based on a really complex system of giant pulleys and a belt. The arrangement is such that there are no true "gears". Keep it clean if you want it to last.
I agree that 'lifetime fluid' means the fluid will last the lifetime of the manufacturer's warranty. After that the fluid, which is just oil with additives and red coloring, will start to break down and wear out the transmission. Especially CVT transmissions with belts inside.
Look in the cars owner's manual and buy the exact transmission fluid it recommends from a brick and mortar Subaru dealer in your area. There's a lot of online scammers claiming to sell OEM parts, but they're usually counterfeit parts being sold online.
There's only two types of fluids I buy from the dealership. Automatic transmission fluid and differential fluid. Both fluids are uniquely blended with friction modifiers to allow for the right amount of slippage. Especially with an AWD Subaru. I would definitely use the differential fluid recommend in owners manual and buy it at the dealer.
Change the transmission fluid like Scotty recommends. Measure how much you drain out and put the same amount back in.
I think automotive manufacturers started claiming 'lifetime fluid' in order to reduce the number of transmission failures under warranty. Most quick oil change shops were probably under or over filling transmissions, or using the wrong fluid. I've seen many cases of stripped out drain plugs and loose drain plugs after oil change shops. My Sister payed over $1,000 after taking her Jeep Grand Cherokee to Walmart for an oil change because they tightened the oil filter too hard with a wrench and the oil filter housing started leaking oil all over the top of the engine.
Here's a more up-to-date video of Scotty changing transmission fluid. https://youtu.be/yUfOdsZLoCs Here's a video of Scotty explaining why it's a good idea to change the fluid yourself and buy the dealership fluid so you're not mixing two different types of fluid. https://youtu.be/OqK79dHGblE