[urq] Re: Fram vs Mann 200q20v digest
Djdawson2 at aol.com
Djdawson2 at aol.com
Thu Apr 18 13:16:06 EDT 2002
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In a message dated 4/17/2002 9:04:17 PM Mountain Daylight Time,
maximum at weetamoo.com writes:
> I could be wrong (happens all the time) but it is my understanding that you
> always want a bypass valve since it can come into play if the filter media
> fails (or becomes clogged) and will still allow proper circulation of the
> even if the filter (noun) is no longer able to filter (verb).
Personally, I agree with you. A bypass valve is a good safety net for filter
(noun) failure, be it failed internals, or simply loaded up with crud. In
large fleet maintenance operations there has been the tendancy to utilize
filters (noun) with no bypass valve in connection with real-time monitoring
of pressure drop accross the filter (again, noun). At a predetermined
pressure drop point, the unit then signals the ECU, or a "filter-minder",
that it is time for an oil change. The same practice is also often utilized
with air filters. In large operations there are finacial reasons why this
approach can make sense. There are, however, a couple of drawbacks to this
approach (as I see it). First, this method does not take into account
anything else that can happen to oil and filters, other than getting dirty.
Second, in our vehicles we don't have an ECU monitoring oil pressure... we
may keep running them with low oil pressure until it's too late, whereas in a
fleet vehicle a low pressure reading would result in the ECU immediately
shutting down the engine.
So, to make a short story long... if you follow a rigid routine maintenance
schedule for oil changes AND you use the car regularly (meaning in doesn't go
long calender periods between oil changes), it is safe and practical to use
filters w/out bypass valves. The only exception to this would be media
failure to the point of no flow (I've never seen that). However, if the car
is a limited use "toy", stick with the bypass valve.
My conclusion, regardless, has been to stick only with the OEM replacement
filters, simply due to repeated hydraulic lifter failure when using Frams.
Sorry so long, but I HTH,
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