I would strongly recommend to only use fluids for your MB that are approved. Always consult the Mercedes Benz Operating Fluids site. (Previously known as Bevo. You can still type in bevo.mercedes-benz.com, and it will redirect you to the site below.)
If you have spent the money to buy a Mercedes, for goodness sake, then spend the money to put quality fluids in it. Mercedes is very reasonable in what it charges automotive fluid companies, to approve their products, so there are plenty of Approved fluids available for Mercedes.
To put anything in a Mercedes that isn't approved is just a crap shoot. Just like Astro14 said, you may or may not get a good fluid. Why risk it?
You just spent, what, $35k - $40k on your GLC43? And now you want to buy non MB approved fluids, so you can save $30 - $40?
Publication platform for approved operating fluids from Mercedes-Benz
operatingfluids.mercedes-benz.com