Just changed the oil in the 190e (215k miles) to 15w-50 synthetic.
Remarkable difference. Engine is much smoother. Both passengers noticed it immediately, at idle and while driving. Much quieter as well.
I believe there are two reasons .... first the benefits of a synthetic oil which is 50 weight, but also because the chain tensioner probably got pumped up or cleaned out and the engine timing being improved.
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)