I did B service on my W213 Diesel 2 days ago and after service it is still engine oil level shows half only (Half way between min & Max). is this as expected after B service (once in 2 years) that costs £550. still engine oil level is not showing full...? Should I complain to dealer..? I can service cost shows 6L engine Oil seems to have added. My worry is middle of this year I might start getting engine oil warnings. thanks.