In the manual it says you can use:
You might want to find out what (competent) BMW dealers use for the 1M, X5M, and X6M, since I believe they have the exact same oil spec as the M5. I'm reading that 5W-30 tends to be used in the US, but not sure about brand.
I'm not surprised that a dealer thought 10W-60 was needed, sadly. I just hope they'd notice the spec on the oil cap before actually putting that into someone's car....
'16 Cayman GT4 (delivery pics
Gone but not forgotten:
'11.75 M3 E92 Le Mans | Black Nov w/ Alum | 6MT (owned 5/2011 - 11/2015)