Pretty likely to be a lifter. Try 15W-50 Mobil-1 for a couple thousand miles, if that doesn't help, test & replace the faulty lifter(s).
Atif, try the Mobil-1 on your car... with new lifters it should be quiet. No oil treatment of any kind should be needed. I've heard of more than one car that had the noise go away simply by switching to M-1. (15W-50. Did I mention 15W-50?)
