ZDDP levels under GF-4 have now been reduced by specifications which limit phosphorous to 0.8%. I am wondering what impact that has on the oil? the simple answer would seem to be just more wear. But, is it?
After doing a bit of research (here and elsewhere), I found that in simple terms ZDDP is an old, cheap, and very effective anti-wear additive. Exactly how it works seems to be a topic of current research, but the consensus seems to be that it reacts to pressure to form a local deposit on the metal which is very hard and wear resistant. It is a surface lubricant and works metal to metal in the absence of a lubricating film. It does not work well when the surfaces are aluminum as the hard deposit is abrasive to the softer aluminum. There does not appear to be a need for it unless you have metal to metal contact (oil film breakdown).
Under conditions of high temperature and moisture the ZDDP can breakdown and not be available for creating a wear protection film.
Graphs from this link have been posted before on BITOG, and here is the full article.
http://www.practicingoilanalysis.com/article_detail.asp?articleid=477
So this all suggests ZDDP is consumed as part of the normal service life of the oil. In conditions of high temperature, moisture, and metal to metal contact, the consumption rate will be higher.
By my way of thinking what all this points to is that when GF-4 required a 30% or so reduction in ZDDP, this has no immediate effect on wear protection of the new oil. What it does do is reduce the life of the wear protection component, ZDDP by say 30%. By that way of thinking this would seem to imply OCI's of GF-4(SM) compliant oil will be about 30% less than GF-3(SL) oils assuming the same wear protection end point. This of course assumes that one was pushing the OCI to the point of ZDDP depletion. And that may be the case if this graph from the article is accurate at all.
Has anyone else looked into this interpretation of the effect of ZDDP reduction? i.e. it does not mean more wear, it just means shorter oil life if you want the same wear?
After doing a bit of research (here and elsewhere), I found that in simple terms ZDDP is an old, cheap, and very effective anti-wear additive. Exactly how it works seems to be a topic of current research, but the consensus seems to be that it reacts to pressure to form a local deposit on the metal which is very hard and wear resistant. It is a surface lubricant and works metal to metal in the absence of a lubricating film. It does not work well when the surfaces are aluminum as the hard deposit is abrasive to the softer aluminum. There does not appear to be a need for it unless you have metal to metal contact (oil film breakdown).
Under conditions of high temperature and moisture the ZDDP can breakdown and not be available for creating a wear protection film.
Graphs from this link have been posted before on BITOG, and here is the full article.
http://www.practicingoilanalysis.com/article_detail.asp?articleid=477
So this all suggests ZDDP is consumed as part of the normal service life of the oil. In conditions of high temperature, moisture, and metal to metal contact, the consumption rate will be higher.
By my way of thinking what all this points to is that when GF-4 required a 30% or so reduction in ZDDP, this has no immediate effect on wear protection of the new oil. What it does do is reduce the life of the wear protection component, ZDDP by say 30%. By that way of thinking this would seem to imply OCI's of GF-4(SM) compliant oil will be about 30% less than GF-3(SL) oils assuming the same wear protection end point. This of course assumes that one was pushing the OCI to the point of ZDDP depletion. And that may be the case if this graph from the article is accurate at all.
Has anyone else looked into this interpretation of the effect of ZDDP reduction? i.e. it does not mean more wear, it just means shorter oil life if you want the same wear?
