17L/100km... that is a lot. You must be doing a lot of city driving.
Has the fuel consumption been like that since day 1 of owning the car? There has to be some reason why the bad fuel economy.
The car I am going to get is a 2009 so it will have 1 year warranty left. I am considering purchasing extended warranty, but for BMW to sell extended warranty, they have to be making money it. 2010 and earlier vehicles are covered through 3rd party, whereas 2011, BMW covers the extended warranty.
Someone must have done the math to determine the percentage of vehicles coming in for extended warranty work or else the dealerships or 3rd party would not be making money. My brother talked to a mechanic who was been working at a BMW dealership for 10 years and asked him about extended warranty. His reply was; if you want it for peace of mind do it but the majority of issues they see are usually after the vehicle passes 120,000km.
Just giving you a different perspective.