In a message dated 1/4/03 11:05:22 AM, albell@UVIC.CA writes:

<< We would like to inform you about the new long life Volkswagen/Audi spin-on

oil filters W 719/30 and W 930/21.

Due to increased maintenance intervals for new Volkswagen / Audi

applications MANN+HUMMEL

developed and introduced the above mentioned Long life-Filters.

Both filters come equipped with a new advanced filter media that allows the

increase of service

intervals paralleled with better filter efficiency, especially when using

synthetic oils.

Both filters are also equipped with new high quality rubber parts to uphold

the longer service intervals.

They are also resistant against the new generation of synthetic oil. >>

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Alistair,

The service life extension of the filter is not too surprising in view of the
fact that they are targeted for use with synthetic oils. I would suspect that
the filter media is a two or three layer system with different porosity in
each layer to minimize clogging of the media. The outer most surface of the
media will trap the larger particles, passing the smaller ones to the
interior. Think of it as a size exclusion chromatograph!

The second issue will be the treating of the filter media to minimize the
attack of dissolved acids (HCl and H2SO4) on the fiber structure. Often this
strong attack can breakdown the fiber substructure releasing smaller fibrils
and thereby rapidly clogging the rest of the filter.

But I assume that the filter was developed as part of an extended service
life maintenance program. If true, then the key problem to be faced is the
buildup of these dissolved acids (minimized by recent advances in emission
control systems). I therefore assume that inspection of the long-life filter
will find a high porosity ceramic pellet in the path to the filter media.
This pellet will carry a set of low solubility bases to neutralize the acids.
The resulting salts will precipitate in the oil media and be trapped in the
filter media.

I would urge routine oil analysis for anyone who really cares about engine
longevity, and particularly those who are pressing the performance limits of
any engine. Oil analysis is surprisingly inexpensive. In general, you will
probably find that you are throwing away good lubricating material at each
oil change. Modern synthetics are amazing, notwithstanding the derisive
rejection by the superstitious!

Frank