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From the "Lubricating Grease Guide":

Contaminants can deteriorate greases. Unless containers are tightly sealed, prolonged storage increases the possibility that contaminants will enter stored product. The most prevalent contaminant is moisture, which can enter apparently sealed containers of grease, rusting the containers and changing the product. Some greases, such as soda soap greases, tend to soften when contaminated with water. On the other hand, traces of moisture have been known to cause clay greases and calcium complex greases to become firmer.

Appearance changes in storage are not a common problem but can become evident if oxidation causes the surface to darken, if air slowly leaves the product improving clarity, or if water causes the grease to become hazy.

Click here for more information about the Lubricating Grease Guide.

Today's Tip

• A major mobile equipment OEM estimated that an average of 53 percent of all engine failures are a direct result of problems with the cooling system. Periodic coolant analysis, including glycol content, pH, conductivity, inhibitor analysis, visual inspection and resistance to corrosion may be as valuable as routine oil analysis in preventing failure due to the cooling system.

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Q & A

"I recently encountered a situation where we are getting high copper readings from a diesel crankcase oil sample. All other wear metals such as iron, lead, aluminum and chromium readings are low. What could be the cause?"

There are many reasons why copper could be high. The first thing to check is the new oil. Some engine oil formulations contain copper additives so checking the new oil baseline is the place to start. If the oil does not contain copper additives, then wear is more likely.

The next thing to check is other trace and alloying metals, such as tin, zinc, etc. If no other elements are observed, there are two other common sources of copper: bearing metal and the oil cooler.

If lead/tin has been historically low, then it is not the bearing because copper will only show up after the bearing overlay has worn. That leaves the oil cooler as the number one suspect. High levels of copper might be associated with corrosion of the core or passification (especially with new engines). If it's associated with passification, the copper levels should go down with subsequent oil changes.

Corrosive potential can be assessed by looking at Acid Number/Base Number and doing a copper strip corrosion test (ASTM D130). One final possibility is galvanic corrosion (due to a small electrical potential, similar to an electrochemical cell). Check the engine grounding if it has electronic controls, also check the engine coolant to determine if the coolant inhibitors are depleted.

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Lube-Tips is published by Noria Corporation. Oil Analysis and Lubrication Experts