Your C240 came from the factory with Mobil One. About three or four months ago, MB announced that they will use Mobil One at their expense for all oil changes in these cars during the 50,000 mile warranty period.
I was planning on showing up for my first service with my own Mobil One for them to use, this announcement saved me the trouble and expense. I change the oil myself between their service intervals and use Mobil One at that time as well.
I would be surprised if you could tell the difference.
Have a great day,