I bought a new 118i in April 2017 and after about 1,000 miles I noticed blue smoke appearing from the exhaust when starting the engine from cold.
The dealer took the car in and and returned it after 3 days saying this new engine has a fault where the rocker-box breather allows oil vapour to pass into air intake for the injection system. The oil vapour then condenses as the engine cools down and when the engine is restarted the oil is sucked into the engine and burns.
The rocker box cover was replaced, along with the spark plugs and the catalytic convertor.
However, the very next day the car was still chucking out smoke when started from cold.
This time the dealer said "it must be unburnt fumes and oil in the exhaust."
For the next few days I made a point of getting the engine really hot, but the problem still persisted.
The dealer has taken the car back in and now they think it may be an oil leak from a burst oil seal in the turbo.
They have been in discusssions with BMW and as yet the car is still with the dealer. Video clip......