If you are not sure bring your key in and they will read it and tell you when your due.. It changes due to how you drive.. I went in a month ago and it said at 12k miles I needed one and now since I drive like a goon I have to go at 10,500...
Hope that helps..
2011 335xi//M series//Injen Intake//BMS 3.5" DP//VMR VB3//Jb4 Stage 2//CSL CF Trunk//AutoCouture Custom Headlights//LTBMW CF Lip