Maynard is right on the mark here. I would add a thing
or two to complete the list (I am an anal, techno-weenie
kind of guy). These are probably not critical for the MG
motors but for larger displacement engines, some of these
parameters can be critical. I know from painful experience!
1. Mounting and space geometry (threads, size, etc.).
2. Filter element particle-filtering size. A filter designed to
trap smaller particles has to have larger surface area to
get the same through-put of oil. Therefore, better filters
require more materials. Thus, they cost more. Cheap
filters are, well, cheap.
3. Some engine designs depend upon the filter being primed
so as to provide an instant blast of oil at start-up. To do
this, a stand-pipe is sometimes fitted to the filter -- especially
when the installation orientation is such that the filter would
naturally drain. In reality, the oil is probably flowing from
the starter action BEFORE the engine actually starts. The
standpipes probably just compensate for questionable
pump designs or filter mounting locations of convenience.
4. Some filters have a by-pass valve to allow oil flow when
the element becomes so clogged as to restrict the flow of
oil. Dirty oil is better than NO oil, I guess.
5. Flow rate. This is filter through-put at the rated pressure
and is related to item one and is usually, in the US anyway,
rated in gallons/minute.
6. Burst strength. This is just what it seems. The maximum
sustained pressure that the canister is designed to withstand.
Associated with this is the strength of the filter-to-engine
seal <when properly installed>.
As for number six; Yes, my 308GTB has blown TWO filters
because of a production run of faulty seals in the factory-
recommended UFI <brand> filters! SIX quarts of Mobil1
pumped into the engine compartment in 10 seconds! What a
mess!
I now use exclusively, Baldwin filters on my 308.
Good sites about oils and filters:
http://subtopics.freeyellow.com/Oil.htm
http://www.vtr.org/maintain/lubricants-redline.html
Oil analysis service:
http://members.rennlist.com/oil/
Best researching,
rick
> There are two main things to consider in an oil filter. First, obviously,
is
> the filtering efficiency (how good the element is). The other thing to
look
> at, is internal construction. There are some filters out there that have
the
> same dimensions and threads, but internal differences. The main thing to
look
> for in this, if you have a top load filter, is if there is a check valve
that
> will prevent the oil from draining from the filter when the engine is off.
>
> Maynard Hirsch
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