Recently had Coupe back to dealer. Service person wanted to do oil change. I have owned the car for 6 months. Warranty books indicate dealer servicing since new. Dealer also did oil change and minor service before my purchase. FSS indicates 8,300km to next service. I advised service person accordingly. He said the oil used started to break down after 6 months and should be changed. I then asked what oil had been used at change. Service person said it was Castrol Magnatec 10W-30 "Dealer Blend". I said that was not the recommended oil. Service person said it was used by the dealership on all vehicles. I then asked about changing to full synthetic oil. Service person said that would require an oil and filter change. A short drive around the block and another oil and filter change. I left the dealership and came home. I e-mailed Castrol and asked about the 10W-30 Magnatec "Dealer Blend". I received a telephone call from a Castrol technician the same afternoon. He said the oil would be Castrol Magnatech FMX. It did not meet the Mercedes Benz specification for use in the engine used in the Crossfire. He recommended Castrol Edge 0W-40 synthetic, which met the specification. I sent e-mail to Chrysler for advice but have not yet received a reply. What is the consensus on the current state of the engine given the Chrysler Dealer has been servicing the vehicle and using Castrol Magnatec? Vehicle still under manufacturer's warranty for 11 months. Any comments would be appreciated.