BMW: bmw 2000 323 i, late model cars, synthetic motor oil

Question
my service engine soon light came on. and i have no idea what can it be . i bought the car 2 days ago and it was fine sisnce then, just tonoght all of a sudden it came on . can u recommend me what to do. thankz  

Answer
John,
 I am not as familiar with the late model BMW's as I am with the older ones.  Since I am not an expert with these later cars, I will try my best.  The "Service Engine Soon" light could be one of two possible things.  It could represent your "oil service" function, or it could be the equivalent to a "Check Engine" light.  
 The "oil service" is an electronic sensor that notes how hard you drive the car, how often, and how many miles you are driving it each time.  It adds all these factors together to tell you when the oil needs to be changed.  Before high-mileage synthetic motor oil (Mobil 1) was developed, the standard for oil changes was "3 months/3,000 miles" which ever comes first.  So if you have a car that sits in the garage all week and only gets driven for 10 miles on the weekends, it would be kind of pointless to change your oil on those intervals.  BMW's system does away with this and calculates when you need to change the oil, based on how much the oil has been used.  When you have your oil changed, the dealership will plug in a small computer to your wiring harness and reset this sensor, where it thinks you have new oil in the car.  Then you start the whole process over again.  If this is what the light represents, you just need to get you oil changed, and the light reset.

 The other option was the "check engine" light.  This light is triggered by a myriad of sensors throughout the late model cars that check for anything and everything.  If this is what the "service engine soon" light represents, then you have something malfuntioning on the car.  I know that if the gas cap is not tightened all the way it will trigger this light as well.  If this light is the one that is lit, then you need to have a "scan tool" to scan the system and see which sensor is malfunctioning.  The dealerships can do this, but are often extrememly expensive.  
 In summary, I think it is your "oil service" light telling you to get the oil changed.  I could be wrong as this is not my area of expertise, but usually if there are malfuntions the "check engine" light burns.  
 Hope this helps,
 Josh