1998 Mercedes Benz S500

Engine problem
1998 Mercedes Benz S500 V8 Two Wheel Drive Automatic 100400 miles

Hi. I recently purchased this car. I have the history and it has run fine. I only put about 1200 miles on it and decided to have it serviced. My mechanic was not sure if it had sinthetic oil previously or not. I have driven it about 10 miles since the oil change and it has developed a velve or lifter tap that it never had before. Could it be due to the wrong oil put in it. I just descovered this noise and it is the weekend so I can not get in touch with my mechanic to ask him what type of oil he used. I went through the previous records and can see that Mobil 1 has always been used previouslly. I do not even know if that is a sinthetic oil or not.

What could be the cause of this problem and what can I do to fix it.
December 30, 2007.

Oiler tubes. There are little caps that pop off these tubes. Remove eight and left valve covers and check if they are missing

Jan 5, 2008.