So I started up a thread a long time ago on this issue, and I got back into researching it. So my 2008 Ls with 73k still rattles on startup, for about 2 seconds. The longer it sits, the longer it lasts. It seems I've found it could be two things. Either the timing chain tensioner, or oil draining back out of the filter (because I guess our cars' filters don't have drainback valves?), and thus the engine is running dry for a few seconds. Don't know much about mechanics, but this seems to be what I've learned. If it's the timing chain tensioner, is it bad, does it need to cleaned, or do I just need to use a thicker oil or something? If it's the filter, are there any good filters that might stop this problem? Perhaps ones that DO have some kind of drainback valve? I've seen a few threads on this topic, but no real answers on how it got fixed. It seems that everyone has bad luck with dealers. Any thoughts? Thanks!