Funny thing, seeing this thread today about the startup rattle.
Since I got my 2015 SHO with 18k on the clock, it has had about a 1/2 second rattle sound on startup. Worse when cold, though it will do it at least a little anytime the car sits for more than a few minutes. But, again, we are talking 1/2 second worth, nothing more.
I always assumed it was "normal" sounds from the engine until oil pressure built. Kind of like a dry engine for a split second that then fixes itself through lubrication. I have heard other cars (all different makes and models) do this too, especially when cold.
But yesterday, I test drove a 2011 SHO with 39k on it (to possibly buy for the wife). That thing was quiet as a church mouse on startup. Even sounded much less "diesel" like when idling than my car does - both warm and cold. Kind of annoyed me
. The wife ended up getting the 4 cylinder Ecoboost Fusion, and that thing is quiet, too.
In the end, I suspect some Ecoboosts will do this a little, some a bunch, some not at all. Probably a "tolerance stack" issue that adds up to create this symptom for X percentage.
