Understanding the causes of engine oil contamination is important to monitor and correct as they are the root cause of premature oil degradation and engine failure.

For example, seal damage resulting in fuel contamination or glycol contamination cannot be remedied by changing the oil or switching to a better quality lubricant. Such symptom-based contaminants are also the root cause of new failures.

To limit engine damage caused by impurities, let’s find out the root cause of this diesel engine oil contamination!

Any of the contaminants described below have the potential to cause premature or even sudden diesel engine failure. Thousands of diesel engines fail prematurely each year due to the presence of glycol, fuel, soot and water in the engine oil.

1. CONTAMINATION OF DIESEL ENGINE OIL FROM GLYCOL

Glycol gets into diesel engine oil through damaged seals, blown cylinder seals, cracked cylinder caps, corrosion damage and pitting wear due to air bubbles. One study found glycol in 8.6% of 100,000 diesel engine oil samples tested. A separate study of 11,000 long-haul trucks found fairly high levels of glycol in 1.5% of samples and small amounts of glycol in 16% of samples.

The following are some of the risks associated with glycol contamination:

As little as 0.4% of the glycol-containing coolant in diesel engine oil is enough to agglomerate soot leading to sludge, solid deposits, oil flow restriction and filter blockage.
According to one study, glycol contamination resulted in 10 times greater wear rates than water contamination.
Glycol reacts with oil additives causing precipitation. For example, an important anti-wear additive in engine oils, zinc dialkyl dithiophosphate (ZDDP), will react with glycol to form products that clog filters when the oil is contaminated with glycol. This results in a loss of resistance to wear and oxidation.
Ethylene glycol is oxidized to corrosive acids, including glycolic acids, oxalic acids, formic acids, and carbonic acids. These acids rapidly reduce the alkalinity of the oil resulting in an unprotected engine against corrosion and oil oxidation.
Oil bubbles form from the reaction of the detergent additive calcium sulfonate (found in most engine oils) and glycol. These bubbles are the cause of damage to the crankcase bearings and other friction surfaces in the engine.
Glycolic contamination significantly increases the oil’s viscosity, reducing its lubricating and cooling properties.

2. CONTAMINATION OF DIESEL ENGINE OIL FROM FUEL

Frequent engine starts, excessive idling, and cold operating conditions can lead to mild oil contamination problems. Severe contamination (in excess of 2%) is associated with leaks, faulty oil injectors and poor fuel efficiency. These are symptoms of serious conditions that cannot be corrected with an oil change. According to one reference 0.36% of total final fuel consumption is in the crankcase. Fuel contamination problems also include wax formation during cold start which can cause low oil pressure and lack of lubrication.

Diesel fuel carries unsaturated aromatic molecules that are strong oxidizing agents into the engine oil. This can lead to a rapid decrease in alkalinity (loss of anti-corrosion protection) and oxidation thickening of the engine oil causing deposits.
Fuel contamination can reduce engine oil viscosity from 15W-40 to 5W-20. This reduces the thickness of the critical oil films in the combustion zones (pistons, washers and bushings) leading to premature wear in these areas and wear of the crankshaft bearings.
Fuel contamination from faulty injectors often causes oil washout on cylinder liners, which accelerates wear of rings, pistons and cylinders. It also increases the leakage of combustible gas into the crankcase and increases oil consumption (retraction from the crankcase).
Severe fuel contamination dilutes the concentration of oil additives and thereby reduces their effectiveness.
Fuel adulteration from biodiesel can lead to more serious problems than usual compared to diesel refined from crude oil.

3. CONTAMINATION OF DIESEL ENGINE OIL FROM SOOT (SOOT)

Carbon black is a by-product of fuel combustion and is present in all diesel engine oils in use. Soot is contaminated with engine oil due to the leakage of combustible gas during engine operation. While the presence of soot is normal, the concentration and condition of the soot can be abnormal, indicating an engine problem and/or the need for an oil change. The following are some of the problems associated with soot contamination:

Fuel combustion efficiency is directly related to the level of soot formation. Improper ignition timing, clogged air filter and excessive ring clearance cause high amounts of soot. Problems caused by burning fuel cannot be resolved by changing the oil.
Newer diesel engines are designed with higher injection pressure to reduce emissions. This corresponds to an increased susceptibility to wear due to carbon black. Exhaust gas recirculation (EGR) on diesel engines amplifies the amount and wear of soot.
The viscosity of engine oil increases with the amount of soot. However, some modern engine oils are highly dispersible which can increase viscosity even more. High viscosity corresponds to cold start problems and the risk of oil shortage.
Soot and engine sludge build up or separate from the oil in the control box, cylinder head, oil pan and engine cover all of which have the potential to affect reliable engine operation.
The deposits on the engine surface affect the combustion efficiency and the ability to save fuel/oil.
Carbon soot removes the anti-wear soap film in thin film lubricating areas such as cams and cam pushers.
Carbon buildup from the accumulation of soot and deposits in the ring grooves can cause rapid wear of the rings and cylinder walls. This can cause the rings to break or be severely damaged in cold starting conditions.

4. CONTAMINATION OF DIESEL ENGINE OIL FROM WATER

Water is one of the most destructive contaminants in most lubricants. It attacks additives, causes oxidation of base oils and interferes with oil film formation. Here are some additional considerations about water contamination:

Long idling in winter causes condensation of water in the crankcase, leading to loss of alkalinity and surface corrosion, oil oxidation, etc.
Emulsifying water can remove additives, soot, oxidation products and sludge. When pulled with oil, these spherical slurries can dislodge filters and restrict oil flow to bearings, pistons, and valve mechanisms.
Water increases the corrosion potential of common acids found in engine oils.
When one of the above causes of oil contamination is not noticed and corrected in time, engine life can be shortened from 750,000 miles to 300,000 miles. Thus, we need to pay attention to maintenance and monitor the condition of the engine oil regularly to control and limit impurities in the engine oil, to avoid operating problems and engine damage.

EPILOGUE:

Hopefully, the sharing of Hawaii Oil will help you better understand the causes of diesel engine oil contamination, and then take timely remedial measures so that the engine can operate at full capacity and increased longevity.

If you have a need to use or learn about lubricants for diesel engines, please contact the hotline below for advice and support as soon as possible:

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