Hello,
I would try to use a "better" oil, the problem could be that the oil isn't gette in where it should. 110K is nothing for that engine. I would try a 5 - 40 oil. I'm using a castrol 5-40 on my 124 - 230 CE from 90' with 150K miles on it. W15 oil is for old worn engines ;-) not a 110K mb engine, you only just broke it in.