I recently purchased a 2018 Sportage and want to do a full flush/maintenance from A to Z by replacing all fluids with top brands and synthetic as well. 
I found that there are three options for differential fluids:
https://www.searchforparts.com/oil-change/kia-2018-sportage-2.4l-c
not sure which to pick, there are three weights and a bunch of info on capacities for each, too much to type/copy paste, this is confusing, the engine oil is straight forward which is 5W-20 for the engine, any input welcomed! thank you