2003 S430 base that sounds like a diesel. on 2003 Mercedes-Benz S430

The car performs great otherwise. The noise seemed to start when I put some regular gas in it one time even though I have used ultra premium ever since. Am I in big trouble?

1 answer 2 comments
What kind of oil do you use? When was the last oil change?
Thanks for your reply. I do not know what kind of oil is in there or how old it is but it looks dark purple and syntietic. I bought the car 4000 miles ago (112k now). Because I did not know the answer to that question I have scheduled an oil change at a Mercedes shop for tomorrow.
You're welcome.
You have to use the right kind of oil in those vehicles. They're very sensitive. I have the same car. You have to baby them.