What is Your Fluid Telling You?

Get to know your metals
Some of the most important parts of the report focus on wear metals and contaminants, additive metals and physical properties of the fluid.

Most labs will separate wear metals and contaminants to identify foreign material that comes from internal (cylinders, pistons, etc.) versus external sources (dirt, fuel, water, coolant, etc.). This will give you an indication if a problem stems from, say, wear in the bearings or from a plugged breather or coolant leak.

In many cases, lubricant suppliers will add certain metals in the form of oil additives (anti-wear and anti-foam agents, friction modifiers, etc.). When you send in a sample, it's important to specifically identify the oil so the lab can cross reference these additives to determine if "good" metals are depleting or if "bad" metals are increasing. "Wear metals and contaminants are related to what's happening with your equipment, and additive metals are related to what's happening with your oil," says Bell.

"Get to know the data," says Mark Minges, CEO at POLARIS Laboratories. "Look at the numbers and become familiar with what they mean."

The lab should be able to provide you with a reference library that identifies each metal with a possible source component. In some cases, the list is printed on the back of the report or you can find it on the lab's website. For example, an increase in iron typically correlates to wear in cylinder liners, whereas chromium is related to piston rings, etc.

"This gives you an idea of what an elevated reading could possibly mean," says Ewing.

Wear metals are reported in ppm (parts per million), and each metal and each engine manufacturer has a different condemning level. For instance, there will likely be higher levels of iron allowed in a sample than lead, since iron is a base metal in so many engine components. Also, a Detroit Diesel engine will likely have a different condemning level for metals than a Caterpillar engine.

This is why it's important to provide make and model information to the lab when you send in a sample, Betner emphasizes. It can also be beneficial to find out the condemning limits from your manufacturer.

"The lab may have generic condemning limits," he says. "But by finding out the condemning limits for the manufacturer, you can marry the knowledge of the lab with the knowledge of the engine builder. It's like blood pressure for a person. While 120/80 is average, it isn't necessarily normal for a particular individual. It's very difficult to customize condemning limits for every manufacturer, and it's nearly impossible to customize them for every customer."

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.