Wear Metals

Iron, Chromium, Molybdenum, Aluminum, Copper, Lead, Tin, Nickel, Vanadium and Titanium

One of the least understood concepts to the layman is "wear metals". They are the first ten metals we list on our report (other than, occasionally, Zinc or Magnesium) and they simply represent the amount of each metal detected in the lube at sampling time, though not the chemical form. As an example, when iron is reported from the plasma emission spectrometer (the instrument used to detect and quantify metallic elements), we do not know if it is in an oxide form (rust) or if it represents relatively recent erosion of an iron containing part in the system.

Within reason, the amount of each metal detected is irrelevant as long as the amount deposited in the lube remains at a constant, stable rate with respect to time or mileage on the lube from sample to sample. For example, it is possible that metal quantities will climb the longer a lube remains in the unit. Under extended drains the values may become further elevated, but may still be indicating a "normal" wear pattern for the particular unit. It is when the wear rate established for a given unit increases significantly that corrective action or inspection may be advisable.

Each unit make exhibits particular tendencies. Some tend to show metal increases at constant rate, while others tend to stabilize after various time/ mileage plateaus. There are numerous reasons why this is so, even between models of the same manufacturer. Among them are lube consumption rate (probably the most significant), sump capacity relative to surfaces lubricated, standard original equipment filtration, whether the unit is supercharged or not, and the BMEP (Brake Mean Effective Pressure; applicable to reciprocating engines) rating. Even identical units may show quite a variance from age difference (lube consumption), special after-market filtration, application, and type of lube.

The moral is: Don't assume that a given unit must have a predetermined threshold value for wear metals, even for a specific interval. Let the trend serve as an indicator.