Please excuse any wrong terminology as I'm not a mechanic
On initial startup, sounds like there's marbles rattling around in there (don't remember where the indy said he thought he heard it). Lasts for 4-5 seconds and disappears.
Cause: maybe oil drained out and not getting in there till it's "filled up" with oil while the engine running. Maybe it's damaged lifters (who knows why). This happens when the engine is cold or warm.
Not fuel related (as i get 40MPG).
What I think is the reason. Either:
1)I did buy her used and quite possibly infrequent oil changes caused build up that caused the lifters to stick at start up. Until the oil gets in there, they "rattle" for that 4-5 seconds.
2)with the cyl displacement I have, with 4 of 8 cyl shutting down in C mode at highway speeds, it just gets gummed up from "lack of firing". I doubt it's 4 "different" cyl shutting down, it's the same 4 every time.
Solutions (well, not solutions but opinions) that I have found (on this site and elsewhere):
There are lots of oil additives out there (and not so much additives as "I've done this and it works fantastic"). Other than commercial "lifter cleaners" (so many of them and they all have equal "positive" and "negative" opinions), some have suggested adding a quart of ATF (or even totally refilling the crankcase with ATF ) , run it for X miles and do a complete oil/f change.
Theory here is it has more "cleaners" than regular oil. NOT doing this.
One other idea I came across (and I'm going out to try this shortly) is to run her at about 3000 RPM for an hour or so.
I would try this on the highway by only running in S (so the 4 cyl don't shut down) and then downshifting till the RPM's hit that 3000 figure.
Comments are most welcome (neg comments are also welcome).