Quote:
Originally Posted by Backhill1
Skyship, yes we carry out a full analysis at 25hr intervals and have a live particle counter in the system all the time.
I still don't understand how you have established dirty filters are better than clean which was my question and how this has been established.
As already mentioned there are to many variables with one engine or duty cycles to establish real effects unless conducted over test conditions.
I'm not sure if you work in tribology or the oil industry or are quoting on your own vehicle?
I have worked for many engine manufacturers throughout my carear and all practices for each are very similar. Most of the best by German and American manufacturers.
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I did work for ZF for over a year, although that was in the bearing wear analysis part of the fluids lab. That was where I was told about Ceratec and the fact that many engine oil companies have removed Moly(Mo) from their oils due to cost considerations, although it's not needed in a German standard (Group 4) Synthoil or GTL base oil (Shell Ultra).
You can't simulate real life in test conditions, which is why ZF and VW have cars and a bus driving around to check on the Lab results.
The big questions are always about how long in both time and distance terms an oil filter can be used safely before it blocks and unless it's a synthetic media or one that can be pre-filled the manufacturers look for the longest figure possible. Oddly enough the limiting factor has often turned out to be the oil filter oil seal, hence the present 2 year limit in the newer OLM units.
In particle or UOA test terms they look at 2 points, one just after the filter and the other just before the turbo inlet pipe, as it still seems to be that turbo bearings and head gaskets are the limiting factor, unless it's a larger marine diesel (Much more expensive bearings). ZF also do oil lab work for both MTU and VW, although they don't have to fit the radioactive parts required for some tests.
I will try again to explain why new full flow car oil filters work better when dirty (Unless they are pre-loaded synnthetics or you can fill it first due to under sump mounting point).
New the Far Eastern cardboard media has lots of tiny holes and the empty filter causes a loss of oil flow on first use. That combination results in new oil dumping extra wear particles into the oil and the average pore size is not good enough to trap the ones that get caught in the bearings (Big particles don't matter so much).
BUT once some sludge and other debris has gone through the filter, many of those holes are partially obstructed. That allows smaller particles to get caught by the remaining partial pore holes.
The oil flow rate is of no real interest, as it's particles that cause the damage, so unless the filter gets blocked or the pump inlet screen blocks (Or varnish formsin the turbo inlet pipe), the slowly reducing size of those holes increases the filters efficiency.
Synthetic media filters are better because the pore size is more random and they use some extra additives soaked into the weave to offset the effects of the higher amounts of active detergents (I think only Mobil 1 filters are doing that at present, as their oil is a tad too effective when new at cleaning).
Oddly enough driver style can make a big difference to some oily figures. Blackstone Lab recorded the record a few years ago, with a 16 year old Nissan pick up truck that had never had an oil or any of the filters changed in over 163K miles. The engine was in real good condition due to the following:
1/ It had an expensive factory fill full synthetic still in use.
2/ No one tried to change any of the filters, so both the air and oil filter were nearly blocked.
3/ One of the injectors gummed up or blew a tip out and this really saved the engine, because the detergent additives in the oil had run out, but it had only thickened from a 5w30 to a 15w40. The only reason that it was not off the scale was that the Bio diesel contamination from the failing injector had offset the sludge formation to a large extent.
4/ The air in Montana is very clean and they don't salt the roads, the driver also pre-heated the engine in winter, although he was doing a lot of local trips.
That old engineer sure knew how to drive!