See also:

Kia Soul owners manual
...

Brake/clutch fluid
Checking the brake/clutch* fluid level Check the fluid level in the reservoir periodically. The fluid level should be between MAX and MIN marks on the side of the reservoir. Before removing th ...

Rear differential (4WD)
Checking or changing rear differential fluid Have rear differential fluid checked or changed by an Authorized Kia Dealer according to the Maintenance Schedule at the beginning of this section. ...