My son just bought a used 2018 Volvo S60 Cross Country with 22,000 miles. It has the 8 speed automatic, Aisin, I believe. I stopped by the dealer to get quotes for replacing ATF, transfer case fluid and differential fluid. Two service guys and one mechanic strongly cautioned me not to change the fluid. Ever. Something about the transmission adjusting to the changing viscosity of the fluid... This sounds like absolute nonsense to me, but they were adamant on this, saying they've seen too many problems caused by changing the fluid. I'm thinking about doing drain / fills at around 50 or 60k with factory atf, but don't want to give my son bad advice. I will be eternally grateful for your thoughts!