What Are The Worst Diesel Engine Oil Contaminants That Cause Engine Failure?

If you own, operate or manage a fleet of trucks, it makes sense — operationally and financially — to have samples of used diesel engine oil analyzed regularly to detect the onset of the worst diesel engine oil contaminants.

Analysis can tell you how well engines are operating and their general service condition. It will also yield diagnostics to help you spot problems before they lead to engine failure.

Particles of Dirt are possibly the worst diesel engine oil contaminants.

It is critical to keep diesel engine oil free of dirt or particulates. Foreign particles are the worst diesel engine oil contaminants and prevent the oil from coating and clinging to wear surfaces. Also, particulates in engine oil become abrasive agents that accelerate premature wear of components.

While better filtration systems on engines, oil storage, and maintenance practices have minimized the threat of dirt contamination, it still remains the biggest threat to engine life.

“It is worth noting that problems are more pronounced when contamination combos exist,” says Jim Fitch of Noria Corporation.

An example of this would be dirt particles combining with water to form miniature dirt balls that can greatly reduce oil flow to critical parts. He warns there are no additives in engine oil that control or minimize these contaminants.

Water is often not recognised as one of the worst diesel engine oil contaminants.

Water is often diesel engine oil's worst enemy. At the molecular level, water attacks the additives in oil that keep engines running smoothly, and interferes with the oil's ability to properly coat component surfaces. Moisture combines with acids in the oil and becomes corrosive, thus hastening engine wear.

Water in oil can emulsify, picking up dead oil additives, soot, oxidation, and sludge to create globular pools that can knock out filters and restrict oil flow to bearings, pistons, and the valve deck.


Also, the water in oil can react or combine with soot, spent additives, or particulates to create globules that foul oil filters and reduce oil flow to valves, pistons and bearings. Even though low levels of moisture are common in engine oils, higher levels are symptomatic of a serious problem — one that might not be solved by a simple oil change can cause the worst diesel engine oil contaminants.

Low levels of water contamination are normal in engine oils. But high levels of water showing up in an oil sample analysis is a red flag that your engine has a serious problem that won't be cured just by changing oil.

Fuel Dilution and soot are commonly lead to the worst diesel engine oil contaminants.

Under certain conditions such as excessive idling, cold running and frequent starts and stops, fuel may find its way into the engine oil and causing some of the worst diesel engine oil contaminants.

Fuel mixing with, or diluting in, oil not only occurs but also can get bad enough to drop oil viscosity from, for example, 15W40 down to 5W20 in a short time, accelerating piston ring, liner, and crankcase bearing wear. In severe contamination cases, fuel dilution thins the concentration of oil additives, weakening their protective effectiveness.

Severe (> 2%) fuel dilution may be caused by poor combustion efficiency, faulty fuel injectors or other leakage. Fuel dilution can drastically alter oil's viscosity (and hence its flow) and can accelerate wear on piston rings, liners, and bearings.

Soot is a by-product of combustion that's present in all diesel engine oils. Excessive levels of soot, however, indicate poor combustion performance and need to be corrected. Soot can accumulate and form deposits on and around engine surfaces, eventually compromising engine performance and reliability.

High soot and sludge levels may indicate poor ignition timing, a spent air filter or excessive ring clearance. These possibilities should be checked out and, at the very least, an oil change is called for to control the worst diesel engine oil contaminants.

While the worst diesel engine oil contaminants are often beyond the scope of lubricating oil to control, high quality full synthetic lubricants such as those produced by Habot Oil offfer significant protection against the worst diesel engine oil contaminants.