In this case your oil change is free. You pay nothing for scheduled oil changes or any other maintenance except wearables such as brake pads and tires for the first 50,000 miles.
I change my oil at my own expense between the FSS intervals. When the light comes on, the change is on them, zero dollars for anything. If you want to use your own oil brand, such as Mobil One you will have to take it to them with the car. But dino oil is free.
Check it out,
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in