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External contaminants

External contamination will show up on the report in the form of elevated levels of silicon, sodium and potassium. If you start seeing high amounts of silicon, dirt is likely entering the system through dirty air filters and/or oil. Sodium and potassium are found in coolants and antifreeze. If they start showing up in an oil sample, it's a good indication there's a leak that may be letting coolant into the system via a blown head gasket, cracked head, etc.

"The historic offenders that can kill a component are dirt, coolant, fuel and soot," says Betner. "These contaminants can lead to catastrophic, premature failures and can bring down a component and destroy the lubrication quality of the oil the fastest. But oil analysis clearly has information present that identifies these contaminants to minimize those failures."

Some of these external contaminants will also change the physical properties of the fluid, which will also be identified in the report. "Viscosity is probably the most important physical property of the oil that you'll want to monitor because it influences proper lubrication," says Betner. "If it's too thick, it won't flow when it's cold. If it's too thin, it won't adequately protect the components."

Viscosity of engine oil can change via several offenders. For example, raw, unburned fuel that has gotten into the oil through a worn or damaged injector or fuel pump will dilute viscosity. Conversely, soot (linked to increased iron) and coolant (identified through elevated sodium and potassium) will cause rapid oxidation and thicken the oil. This shows up as increased viscosity.

"If viscosity goes up too much, it will start to plug oil galleys, which will cause the engine to fail due to lubrication starvation," says Papacek. "Also, because of the nature of coolants' corrosiveness, it will begin to attack soft metals, such as main and rod bearings, which are made from lead, copper and aluminum or tin. The coolant washes out the bearings and takes the crankshaft with it. Soot, which is a byproduct of improper combustion caused by inadequate oxygen, will cause elevated iron levels from wear on the engine. There's a direct relationship between just about every contaminant and every component, so it's important to understand the relationship between contaminants and wear."