Anybody else hear pinging or knocking with their V6? I should start out saying I really don't know if it's pinging since I've never actually heard what pinging sounds like. I've heard it described as marbles in the engine when the engine is working hard.

This sound started about 3-4 months ago and I noticed it mostly when commuting on surface streets. It only happens when going about 30-50 mph when the transmission has up shifted so the RPMs are fairly low and the engine is almost lugging. It does not happen, or at least I can't hear it, when I take off fast.

I've run 87 octane ever since new and never heard it. I switched to premium a couple months ago and it seems like the sound has gotten better in the past 1 month.

When I took it into the dealer a few weeks ago I did a ride along with the mechanic and he said these engines are known for pinging, but he could not replicate the sound.