The oil analysis report we received from our lab showed elevated levels of sodium and potassium in our engine oil. This oil has also become significantly thicker. What could be causing this to occur?

There are multiple sources for the sodium found in your diesel engine oil. Based on your operational environment and equipment type, you should be able to narrow this down to a smaller list of causes. Potential sources of sodium include coolant, salt water, additives, grease thickener, base stocks, dirt and road salt.

On the other hand, potassium has only one real major source when found in engine oil — antifreeze. Other key elements that you will want to look for are boron, chromium, phosphorus and silicon. All of these elements are associated with antifreeze and, if found in engine oil, can be an indicator that you have a coolant leak.

The causes of this coolant leak will take some investigation. Trouble areas include defective seals, electrochemical erosion, cavitation erosion, corrosion of the liners, a damaged cooler core, a blown head gasket, or a crack in the cylinder head or block. The effects of antifreeze contamination are a rise in the oil’s viscosity or a thickening of the oil (as witnessed), the formation of gels and emulsions, acid formation leading to corrosion, premature filter plugging and all-around poor lubrication. In fact, glycol contamination is reported to be the No. 1 cause of premature filter failure in a diesel engine and overall poor lubrication.

Another potentially huge problem to be aware of is the reaction of calcium sulfonate (engine oil detergent) with ethylene glycol (engine coolant). When these fluids are mixed, a chemical reaction ensues that produces small abrasive balls as a byproduct. These "oil balls" are between 5 and 40 microns in size. The significance of the size is that this is also the size of the fluid film. In essence what is produced is a sandpaper ball that fits perfectly into the clearance between the engine’s internal components. The results are severe wear and eventual failure.

There are a few ways to test for this mixture. The three basic field tests for antifreeze in oil are the blotter spot test, the patch test and Schiff’s reagent method. If you have access to a lab, you also will want them to run Fourier transform infrared (FTIR) spectroscopy and gas chromatography to confirm a coolant leak.