I just returned from the dealer after having my oil changed for the first time(5000 mi service). I checked the dipstick to make sure they did not add too much oil and the oil is black. Is this normal? I am used to oil looking very light in color immediately after an oil change, but this is my first TDI and my vehicles in the past did not use synthetic oil. Also, my car now sounds louder than it did prior to the oil change.