My SLK goes in for its its first service tomorrow, just coming up to a year old and 7k miles. A service, it says, no problem. The service dept tried to sell me the benefits of hiving some oil flushing and fuel additive, and 'this is good for the car'. I asked if MB recommended this treatment, as it didn't appear to be in the hand book. They avoided a direct yes/no answer, so I declined, and just booked a standard service It sounds a bit like snake oil to me, and I right?