Because they are "run in" at the factory on the engine assembly line.
Many ordinary car engines are too, but probably to a lesser degree.
Your rebuilt engine has to use your Vanagon as the engine stand!

For those of you who have bought engines from Boston Bob or others, what
oil did they recommend?

Terry Kay wrote:
>
> Stuart,
> "Never use synthetic oil for break in?"
>
> Hmmm---wonder how the new Vette's get away with using Mobil 1 direct
> from GM?
>
>   ______________
>  |[  ] [  ] [ ]\
>  |    |    |    |
> ||-(())----(())-|
>
> Terry
> 74 Campmobile (Clementine)
> 85 GL
> 86 BMW 325 ES

--
Stuart MacMillan
Seattle

'84 Vanagon Westfalia w/2.1
'65 MGB (Daily driver since 1969)
'74 MGB GT (Restoring sloooowly)

Personal mechanic for:
'70 MGB GT (Daughter's)

Assisting on Restoration (and spending OPM):
'72 MGB GT (Was daughter's, now son's)
'64 MGB (Son's)

Stripped and gone but their parts live on:
'68 MGB, '73 MGB, '67 MGB GT