Ford EcoBoost engine issues

[Must16]

I have an 2016 Mustang with the 2.3 motor. I have been checking the coolant level which has dropped from half down 50mm lower. Also checked the oil filler cap and its got an oily sludge on the inside. The exhaust blows white smoke (not excessive but stops after a while) I bought the car 2weeks ago and its still under dealer warranty. This started happening after a week of ownership.
The car has been checked and no leak was found,but its going back this week as the coolant has been dropping level. But lets see what they say when they check the car on tuesday.