Re: Oil filter/Quickie oil changes

[Chris Newbold <cnewbold@transarc.com>]

Michael Murphy wrote:

> Unless Audi has an engine oiling system design that I'm not aware of (a
> distinct possibility) you need an antidrain back valve _only_ if you
> mount the filter w/the filter opening at an angle that would allow
> gravity to drain the filter.  Please correct me if I'm wrong here.

I believe that the main purpose of the anti-drain valve is to prevent
oil from draining out of all of the oil gallies in the entire engine
lubrication system (most of which are higher up than the filter).

The idea is that at start-up there is little delay before full pressure
reaches critical components. Without it, oil drains back down from the top
of the engine, though the filter, and back into the sump; at start-up,
it would take time to pump oil to the top of the engine again.

(Of course this doesn't do anything to stop oil already forced through
the system from draining back through the return passages. This is
why the valve covers aren't full of oil. The important part is that
the supply passages remain primed.)

-Chris
1993 90CS 70k miles