Just this last week I noticed an odd sound at idle at several red traffic lights. It sounded then like a dry, spinning noise. I couldn't immediately determine where in the engine it might be because it seems to echo through the whole engine. At higher rpm would go away. I changed the oil today (didn't see any flecks in the oil, but did notice a little gasoline smell to the oil, and it did seem to have some gas in it)and started it up, but the dry, spinning has turned more like a grinding noise. At 3000 rpm it goes away, and the motor sounds as normal...under 3000 rpm the noise returns. Could that be a timing chain being loose, or does that sound more like a bearing going out inside the engine? Thoughts appreciated.