I'll post this here, since I own a C4. I'd also like to see more action here in the C4 area , since I think this is a great site :) I've always used Mobil 1 in my Vette 'cause that's whats been in her since day one. Now I see Castrol makes a synthetic THEY CLAIM.... is 8 times superior to Mobil 1. Opinions,arguements, mud slinging..anything guys?? come on jump in ,get your feet wet !!