I have a 190D that I've put Mobile 1 in. The car had over 300k on the odometer when I bought it, and I change the oil once ever 5000K, as opposed to the 7000 recommended by most garages. Being a diesel, and running on the warm side, I run 15W50 in it all the time, and the car has no problems. When I was running a lower weight oil, the level off, was about 1.5 on the scale (3 is max) Now, it levels off at around 2, when hot, and idling.
I've also used two different weight oils on a gasoline engine for summer/winter, with a good amount of success.
"And angels shall weep crimson tears for those souls lost through ignorance."