Re: Audi Oil Filters

[zm@mhcnet.att.com (Zafer Mehmood [209])]

> 
> There has been some talk on here about how much better Audi oil filters 
> are, because they have a checkvalve in them to maintain oil pressure for 
> the next startup. Did I understand this correctly?
> Why would this work? The oil will drain through the bearings etc...
> wouldnt it?
> If it DID work, this would imply that the next morning when I turn on my 
> key, I will read a substantial oil pressure (where I left it last night).
> Did I miss something?
> Bob
> 

Oil filters with the anti-drain-back valve do not maintain oil pressure
after the engine is shut off. The just prevent the oil that is in the oil
pipes/passageways above the oil filter from draining back into the pan.
In the case of most Audis (atleast on the 5000 series that we were talking
about) the oil filter is mounted vertically (with the opening facing up).
So the oil in the filter does not drain out either. So, at initial startup
in the morning, the oil pressure builds up much faster and the hydraulic 
lifters, sitting on top of the engine, get their much needed oil sooner.
Hence, little or no lifter noise at startup. The quicker oil supply benefits
the rest of the engine parts too.

I was surprised at the amount of oil that came out of the vertical oil
pipe when I removed the Audi turbo filter in my '87 5000 TQ. It was
about 1/3 to 1/2 quart.


-----------------------------------------------------------------
Zafer Mehmood				   AT&T Bell Laboratories
zm@mhcnet.att.com			   Murray Hill, NJ