Service A is a very basic oil and filter change, plus some checks.
Service B is the same oil and filter change, plus some additional checks. On some models the cabin filter is also included in the Service B schedule.
The car is due a service every 12 months, or 15k miles, whichever occurs first.
It then alternates between Service A one year and Service B the following, and so on.
In either case, any other service items are not included in the service, and will be invoiced separately where these are due. These include transmission fluid change (on automatic cars), spark plug change (on petrol cars), brake fluid change, coolant change (on older cars), fuel filter change, etc.
So the dealer might tell you that your car is due a minor service - Service A - and additionally it also needs to have the ATF changed, or the brake fluid changed, etc.
In general terms, you should go by what Assyst Plus says. However, Assyst Plus needs to be reset when the car is serviced, so it will only provide correct information if indeed it has been reset whenever serviced, and not in between services...
Now I understand the dilemma whether you should go by what Assyst Plus says - which is what would usually be recommended - and have the car serviced in February 2015 - or follow the 12 months schedule and have the car serviced in December 2014.
Personally I would go for December 2014 - but only after seeing a physical printout of the Electronic Service Sheet showing the previous service on December 2013, rather than just taking MB's word for it.
(To confuse matters further.... up until 2007, Assyst did NOT prompt for service every 12 months, but had flexible service schedule meaning that low mileage cars could run far more than 12 months - in some cases even 24 months - before Assyst promoted for next service. But for your 2011 car this is no longer the case, and Assyst should prompt for next service 12 months after having been reset)
