When do you change transmission fluid

100000

My Subaru dealer recommends replacing the CVT fluid every 50,000 miles. It really is not lifetime regardless of what Subaru says.

Every 4 years.

Change transmission fluid every 4 years? What if you have over 100k miles on a 2014 Legacy? My mechanic told me i can ruin my car as “by this time its sealed”

"Sealed"? The 14mm drain plug is very easily removed to partially drain the CVT, but maybe s/he is referring to the tighter 8mm-allen fill plug up on the side...THAT can tale a strong arm or a solid whack to crack.

Sealed means the fluid is likely burnt or has a varnish build up on the clutches inside the transmission. When you replace the fluid it washes that varnish off and can cause transmission failure.

Pretty unlikely on a Subie CVT. First gens just fail re of fluid conditiopn. Second gen seem more durable...so far.