E36: 15W50 Synthetic??

["Nick Pashley" <NickPashley@xxxxxxxxxxxxxxxx>]

Hello list

These questions always intrigue me because BMW give a CCMC / API spec and
required viscosity for the ambient temperature range in the owners manual.
These CCMC and API specs do not necessarily refer to synthetic oils and
hence nowhere in my manual does BMW specify a synthetic oil.

For my E36 325, used in the UK, I use Castrol GTX 15/40 multigrade which my
manual tells me will cover engine operation between -20deg C (-2 deg F) and
30 deg C (90 deg F) and is certified to API SJ spec. (which supercedes the
API SF spec in the manual).

As I work for an engine manufacturer, I can warrant that millions of pounds
are spent every year on testing oil requirements to ensure good engine life.
I am no expert on lubricants, but I trust and will follow the instructions
of those with authority and experience.  Are we, the users, credited with
the experience to say that one oil brand or blend will perform better than
another ?  Do we have the required evidence from controlled testing or are
we spending money unnecessarily ?

I found this site which may be of interest
http://www.geocities.com/chrislonghurst/engineoil_bible.html

Nick Pashley
'93 325i coupe

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