Had the 1st service done on my C63 last week, and I am less than impressed as they have used Castrol SLX oil instead of Mobil1. Ok, it has the 229.5 approval etc but still, AMG recommend Mobil1 and I'm not happy that they've used Castrol. Looks like it was silly of me to assume they would use the recommended one. The damage: £300 Anyway, I am finding it hard to find a top up bottle of this oil as it seems to be one you can only get from the stealers. Would it be ok to use any 0w-40 229.5 oil like Mobil1 or does it have to be Castrol?