2006 Sebring Convertible 2.7
 

Hi Everyone.
I have a red 2006 Sebring Convertible Touring with 2.7 liter motor.
I purchased it about 10 days ago. It has about 90K on it and runs great. When I test drove it before buying it, the motor sounded very quiet. However, all of sudden I noticed engine tapping noise at idle about 4 days ago. A mechanic said to change oil and it may go away or it may be valve lifter noise. Other than the tapping noise, the motor is very quiet so the noise sounds more louder to me.
I did replace oil with Mobil1 Synthetic Extended Performance for high mileage cars, but it did not help. I tried lifter cleaning additive (Liqui Moly), but it did not help either.
I just made 140 mile trip without any issue. I can hardly hear the noise inside while driving. Can I ignore it? Please give me advices. Thanks.