I've mentioned this before, but it seems valid here too. I have supplied my own oil since day one (minus factor fill) when getting my oil changed at the dealership. I always give them 5 liters (the oil I use is sold in liters, not quarts) to use. As I understand 5 liters is equivalent to about 5.3 quarts of oil. The CTD calls for 4.5 quarts if my memory serves me correct. Every time I have the oil changed, I ask for the remaining oil back. With the exception of one time (I've had at least 8 oil changes done), I haven't received oil back. That leads me to believe that they are just using all 5 liters and calling it a day (who knows). When I check the level for myself, it's usually just a bit over the full line. Nothing major, but still over. If this is the case, they have basically overfilled me every time and I have had no issues. My guess is that they are doubling the required amount of oil in some cases (as mentioned in another thread). Going forward, I would mention to the service writer that the car calls for no more than 4.5 quarts of oil. Make sure they note this on their paperwork. It's a PITA to have to do this, but it looks like it could end up saving you a lot of grief in the future.
