New oil=Increased wear?

[Tim]

A bit of an extreme example, but it makes the point:

My Mercedes leaves about a quart of dirty oil behind in the oil cooler and lines with every oil change.

How do you think my early wear metal analysis would be skewed by having 15% of the oil in my "fresh sample" containing 20ppm iron?

If you assume a sample with zero miles should have 1ppm and it really has 4ppm, would you assume the 3 ppm arose from the simple act of changing the oil, or would you suspect some carry-over?

Of course, we would suspect carry-over. And I bet there is some carry-over effect, especially evident on short OCIs, that is not being properly accounted for.


Tim

 

[Gary Allan]

Well, sure you can attribute some to residuals. I'm sure that no oil is perfect and some stuff gets deposited whether you like it or not. So, you probably disrupt some older film that may have locked up some metals in the process ..who knows.

If you wanted to find out you would do a series of 1k OCI and then do a 2k OCI ..followed by a 1k OCI ..followed by a 3k OCI and so one to see of any variance in the metal readings occured. That would rule out any residual theories anyway. They should be reduced to a very low level.

 

[redlm]

I think folks are getting too much information.

Anyway, where does the wear metal go after the oil is "broken in"?

 

[jmac]

redlm, it is still there, what they are talking about is the wear ~rate~, or how much more ppm are added with each succesive x number of miles after the first x number of miles.