My experience with Castrol...
Yes, another oil thread. So, after long time use of M1 0w40 I thought I'd try something different, namely the MB-approved Castrol 0w30. Within a couple of days of the oil change, I began to get lifter noise especially when the car sat for more than a day or so. At first I thought it was due to the cold nights thickening up the oil etc but it's been warm in south TX last several days and this persisted. At this point I had about 500 miles on the Castrol and would get lifter noise on pretty much every cold start. So couple of days ago I changed back to M1 and even though temps were low 30s last night, no lifter noise.
Just FYI, not bashing Castrol, just didn't work for me.