That's the equivalent of a dipstick, not when the car needs an oil change.
When you start the car, you will see a mileage reading which counts down to 0 when you're ready for service) This is what decides whether or not the car needs an oil change. Once it gets to 0, your dash will say "service" very clearly when you start the car.
'15 i3 REX // Capparis // ZGW // ZTD // HK // 20"
20% Tint, Coding, LED High Beams/Signals, Painted Reflectors, MAX2 Hardwire
Past: F30 335i, E90 328xi