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Date: Thu, 03 Feb 2005 17:12:21 -0500
From: Ernest Christley <echristl@cisco.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Oil Filters
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Wendell Voto wrote:

> I used and still have one of thoes tissue paper filters. It worked great.
> Only reason for not using it now is there is no room in modern car 
> engine compartments to mount this by-pass filter.  Did not change oil 
> in car I used it on, just changed filter and added the quart lost when 
> changing paper.
> My impression of oil filters is that they will only hold the "big 
> stuff" that might block passages but do little to really help keep oil 
> clean, hence change oil to get dirt out. FWIW
> Wendell


The experts from the oil companies that I listened to at SunNFun, 
indicated that a big part of the oils job was to buffer acids.  The 
acids are caused by water reacting with byproducts of the combustion 
events.  Sulfuric compounds mostly.  There's always some acid, but a 
regularly used engine will have less (the water is constantly being 
boiled off).  Tiny particles, too small for the filter to catch, can be 
held in suspension and never cause an appreciable amount of corrosion, 
IF the oil is changed when it's ability to buffer the acids has been 
used up.  The counter-intuitive part was that a weekender engine uses up 
the buffers FASTER than a busy trainer, as the weekenders and hanger 
queens don't run enough to constantly boil the water off.  The 
disturbing part is that the oil can be as clear as sulfuric acid, and be 
doing your engine a world of hurt.

Of course, this comes straight from the mouth of the horse that's trying 
to sell you some oil 8*)