Miata Mailing List: May 1994, Message #243
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   From: jwa@yog-sothoth.dcrt.nih.gov (James W. Adams)
Subject: Re: Oil Filters
   Date: Tue, 10 May 1994 16:08:17 -0400

Jim Chu epistolates:
> 
> thing when I used it in the winter time.  I tried Castrol Syntec, but
> didn't mentally like the 5w50.  I felt the range is just too great.  The

The reason the range is so great is that synthetic oils don't thin as
much at very high temperatures, due in part to their homogeneity. 
Natural petroleum oils are a hodgepodge of different molecular weight
oils with varying degrees of branching.  With synthetics, the W number
is generally the one of most interest.  Synthetics generally don't need
much if any of the much-discussed "uncoiling" viscosity improvers.  A
natural petroleum oil with a 5W50 rating would indeed not perform well,
as most 10W40 natural oils fail to maintain viscosity well.

> MR2.  Fram oil filters has been one of the industiry leaders in oil
> filters.  They trapped more smaller particles on the first run than most
> leading filters.  Yes they do have a override valve.  The number is PH
> [...]
> Trak Auto.  Be aware of the cheap filters as they don't have the
> override valve and the filter paper will let smaller particle filter
> thru.

Actually, according to U.S. DOT (Transportation Dept.) and consumer
advocacy group tests in the 1980s, Fram won out by *not* trapping very
small particles.   The net result was that the cheap filters trapped
*everything*, even particles too small to do any damage.  This resulted
in the filter becoming totally clogged in as little as 200 miles, and
the engine effectively running without any filter at all thereafter!
The recommendation was to use either Fram or one of the vehicle
manufacturer's brands (Mazda, Motorcraft, AC, etc.).

> I have my doubts about the quality of the Mazda oil filters... I'm just
> guessing that they contract out to a major company to produce it to OEM
> specs.  I want something better than oem specs.

Auto manufacturers have for years placed great emphasis on oil filter
quality because they can hardly afford having thousands of owners coming
in for new engines under warranty, just to save a few dollars on a cheap
filter.  Mazda filters seem about as good as any quality filter.  There
are industrial filters available that are better, but they are very
expensive and require modifications or adapters for use on an auto
engine.