eSource 103 - Best Guess? HD Diesel Engine Bearings & Sample Information

eSource 103 - Best Guess? HD Diesel Engine Bearings & Sample Information

Posted 12 February 2018

One of the fundamental tests in oil analysis is analyzing data from engine wear metals.  This spectroscopic analysis test encompasses wear metals from the primary oil wetted components.  As the oil circulates through the engine, microscopic wear metals from the engine components become trapped in colloidal suspension within the oil stream.  Monitoring the concentration of these metals can be very helpful in detecting the early onset of abnormal elevated wear and monitoring the wear trend.  Wear metals also can be present in very high concentrations, which may indicate extreme component stress or failure in progress.  

It was not too many years ago, the metallurgical differences in Heavy Duty Diesel Engine components were negligible, as pertaining to used oil analysis.  Of course there were significant differences in design and performance, but most of the engine manufacturers used similar materials for main bearings, pistons, cylinder liners, etc.  In a general sense, knowing exactly which manufacturer and model of engine, was not absolutely necessary to understand where the wear metals came from.  What was (and is now) impacted is the way alarm limits are set and utilized for detecting an abnormal wear condition in a given engine.  

Most engine manufacturers have several models they produce to meet the needs of the marketplace. The various models from a single manufacturer may each exhibit very different wear patterns.  And what levels of “Normal” wear are acceptable for one model may indicate a “Critical” condition in a different model from the same engine manufacturer.  Then, of course, there are unique signatures from each manufacturer.

In the engine models being produced today, in addition to having different wear patterns, some engine manufacturers have gone away from the traditional metals used for bearings, and have begun using completely different materials.  For example, in the construction of main bearings for HD Diesel Engines, the tri-metal bearing was dominant for more than 20 years and is still used in many of today’s engines.   It is composed of a flash layer of lead/tin or lead/tin/copper followed by a barrier layer of nickel, followed by a layer of copper/lead/tin with steel backing.  And then some years ago, engines began being introduced to the market using an Aluminum alloy bi-metal main bearing with aluminum alloy (with or without overlay) and steel backing, with no lead alloy whatsoever.  

So, what this article is leading up to is this: how can the lab diagnosticians interpret the wear metals in your sample without knowing which engine make and model the oil came from?  We can make an educated guess as to what the test results are telling us, but do you really want that kind of report?


We continuously solicit this information and provide our customers several options for providing the information; using the online database to pre-print jar labels and supply the information, using the sample information forms which are easy to fill out, customers may provide either electronic or printed spreadsheets listing the engine make/models of their fleet and send to Customer Service in the lab. The Diagnosticians when evaluating a sample condition with no engine information will often ask the customer to please supply the missing information on the next sample.


Every one of our customers wants to have a successful program that reduces failures, provides insight to what is needed at the next scheduled maintenance opportunity, and ultimately reduces maintenance costs while improving equipment readiness.  Working together we can accomplish this.


Written By:

Jonathan H. Sowers  CLS
Senior Diagnostician, Tribology
North America


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