OIL ANALYSIS OF AN ENGINE OIL – CONTAMINANTS

Water is one of the most destructive contaminants for lubricants as it corrodes iron/steel surfaces, accelerates corrosion, depletes and degrades lubricant additives, promotes lubricant oxidation and reduces lubricant performance.

Water also reacts with some additives and precipitates forming chemically aggressive components such as sludge, it also promotes the development of bacteria that accelerate oil decomposition.

Possible causes of water contamination can be:

• Use of oil contaminated with water
• Leaks in cooling systems
• Condensation in oil tanks

The quantitative content of water present in a lubricating oil sample is usually determined by the Karl-Fisher titration method.

Most engine oils undergo some fuel dilution during operation. An overextended oil change, improper operations, or engine malfunction can lead to a buildup of fuel in the lubricant.

Fuel enters the crankcase as combustion residue and leaks. Gas leakage (“Blow by” effect) occurs because combustion may be incomplete or inefficient, and this fact may occur due to:

• Driving in neutral (neutral)
• Faulty injection patterns
• Improper air/fuel ratio

Fuel dilution adversely affects lubricant performance in the following ways:

• Accelerating oxidation: Fuel molecules oxidize very easily
• Loss of lubricant viscosity: The fuel, being miscible with the oil and having a very low viscosity, causes the lubricant to noticeably reduce its initial viscosity.
• Additive dilution: as the fuel does not have additives, the lubricant's own additives are proportionally diluted, thus losing their effectiveness.
• Accumulation of sulfur: the sulfur present in the fuel increases the risk of corrosion.

One of the tests that can indicate that the lubricant has been contaminated with fuel or other volatile elements is the flame point test. The test is done by placing the oil in a cup placed under an open flame. The oil in the open cup is gradually heated and its temperature is measured. The temperature at which the fluid gives off enough vapor mixed with air to produce a spark at the oil surface marks the end of the test. An oil diluted with fuel will burn faster than an uncontaminated oil.

Soot is a natural by-product of combustion. Long oil changes or poor combustion cause an abnormal buildup of soot, which has damaging effects on the lubricant and the machine.

An accumulation of soot in the oil can cause incorrect lubrication and therefore generate deposits or sludge. In addition, it must be taken into account that soot is abrasive and its presence can cause abrasive wear of the lubricated components. It is normal to indicate a high concentration of soot when there is an amount greater than 2-5% in the oil.

All motor oils are added with dispersing agents in order to control the agglomeration of these soot particles, and therefore the unwanted formation of deposits or sludge, but extended use of the lubricant can cause these dispersing agents to run out and not perform their function.

Soot build-up can be accelerated by the following factors:

• Improper air/fuel ratio.
• Low quality fuel with higher amounts of sulfur.
• Extended oil change intervals.
• Problems in the injection system (worn or poorly adjusted injectors)

The amount of soot present in the oil can be determined by FTIR spectroscopy or by viscosity, since as the presence of soot increases, the viscosity will tend to rise.

The glycol (contained in the coolant) is introduced into the oil through the cooler. Corrosion leaks, seal failure, cooler damage and cavitation are the most common causes of glycol contamination.

Glycol is extremely harmful to lubricants, filters and the engine for the following reasons:

• Induces oxidation and the formation of gels and emulsions
• Increases oil viscosity
• Forms oil balls that are abrasive
• Prematurely clogs filters

It is important to control the entry points of the glycol to avoid this contamination. In the event of severe contamination by glycol, it is always advisable not to change only the engine oil, but to clean the engine and the oil tank beforehand.

It is possible to detect the presence of glycol in the oil by the presence of water, boron, potassium and/or sodium.