just bought a 2017 S60 used and super cheap, although it looks like it went to hell and back, gonna fix it up, has 79k miles on it, not too shabby...

I don't plan on going to the dealer and a good friend has a garage with tools and a lift, so I am good there, plus he will help me out, I bought replacement belts, and plan to change all fluids, but noticed a severe gear lube available, see here:
Best recommended synthetic oil for your 2017 Volvo S60. Save money on oil changes, avoid costly auto shop visits with the best synthetic oil, filters, transmission oil, coolants and differential fluids on the market! Drive 15,000 to 25,000 miles or 1 year!

it says it is for the differential, I looked that up, it's basically rear axle oil?? I always have known to change the oil, transmission, brake fluid, power steering, but ya never hear "hey change the differential oil"

so is it worth it, from what I see it looks like a bit of work, really don't want to mess with something I have no experience with, opinions welcomed!