Hi Dan,
I can only speak about the new Lycoming engine.  My new 0-320DIF was
installed, made the first flight (after some moderate ground runs) and
did not use any oil during the 'break in' nor has it used any since
(between 25 hr changes).  I'm a 'graduate' of the Lycoming engine school
and while there I learned that all their new engines are run in a test
stand for an average of two or three hours so it does not suffer from the
initial break in required of a newly overhauled or 'topped' engine.
Lycoming stresses frequent/regular use and frequent/regular oil changes
to make the advertised TBO.

I've also attended engine forums at Oshkosh and was told (after much
pressure and pointed questions)by a Lycoming rep conducting one that the
only 'problem' one could have from an engine not properly broken in was
increased oil consumption during the normal life of the engine.  IMHO a
small price to pay for sticking to a conservative, safe flight test
program.  And mine does not use excessive oil after using that approach.

Keep in mind this is only my conclusion drawn from watching and
listening.  Earl 235/320  N233E

------------Dan wrote-------------
> The reverse is true of a  new engine
> in that it needs to be run at high power settings to seat the rings
and
> properly break in the cylinders.  So what do you engine guru's have  to
say?  
> I've never done either break in, i.e. new plane or engine.
>