It's not a big deal at all, really. It's done it since we got it in June. When we start it, there is a small rattle (like a chain vibrating) for about 2 seconds. It's not anywhere extreme, like the 2.4L problems Doesn't sound nasty at all. Done it with the OE ACDelco filter, and Purolator PureONE filters. Just curious if anyone knows what it is? It's the 3.0L HFV6.