"top gear" wrote in message
...
":::Jerry::::" wrote in message
...

snip

So why are they not specified by the people who design / make the
engines
?

The makers specify an API rating. It is on the side of the can, Some makes
do specify synthetic oils.

I know that, but it doesn't answer the question as to why the makers don't
spec' full synthetic oils if their engines would benefit from the use of
such oils...


IMM, you were proved wrong the last time you spouted this marketing
bollox
and you will be proved wrong again.

You have me mixed up with someone else, and you are not the first on this
news group to do so.


Well, you certainly quack like him....