Yes, it is lifter noise. My '01 E55 had it, my '01 E320 has it, and my wife's '04 SLK32 has it. Oil in all has been Mobil 1 0W-40 synthetic and has been changed at 6K mi. Hard to believe but unless I purchased three cars with defective lifters it seems to be the nature of the M112 and M113 engines in my experience. Mark