I-5 Lifters and Marvel Mystery Oil

["Christopher Ritchie" <cjr1@gte.net>]

The lifters on my I-5 engine are noisy at start up.  The noise goes away
after the engine runs for a few minutes.  I am using 15W-50 Mobil 1 in the
summer and 10W-30 Mobil 1 in the winter.  This is in New England.  The oil
is changed every 3-5K miles along with the Audi OEM oil filter.  Adding 1/2
quart of Marvel Mystery Oil ("MMO") will quiet the lifters right down.
However, they go back to their "clicking and clacking" when I change the oil
if I do not add more MMO.  I was hoping that a one time application of MMO
would clean out any gum and varnish from the lifters so that they would
operate quietly from then on.  No such luck.  I do not mind adding the MMO
at every oil change.  But I wonder what the long term effect will be.  Am I
just thinning the oil?  Or does MMO really have magical properties with
regard to lifters?  After spending a premium for synthetic oil I would like
to get the full benefit from it.  Adding an additive just does not seem
right.  Maybe this is just my prejudice against oil additives.  Any
experience from long time MMO users?