Been noticing a knock or pinging sound from our 2015.5 XC60 T5 after a cold start. I can somewhat hear it when idling, and the heavier the load when accelerating, the louder it is. It only last a few minutes. I have about a 1 mile drive to the highway on 45mph road with 4 stop signs. About halfway to the highway I start to noticed the noise abating, and by the time I hit the on ramp it is gone. Is this normal, or something to be concerned about?

 

It may be as simple as low grade gasoline. Try using a mid grade (if available) or a different brand.