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Understanding Oil Contaminants

By Tom Bock

September, 2017

There are numerous contaminants that effect motor oil. There are the well known ones like dirt, sand, soot, water, glycol, fuel and acid but few realize that oxidation and nitration can prevent the additives from performing properly decreasing useful oil life.

In both oxidation and nitration there are chemical reactions of the oil molecule with oxygen or nitrogen from the ambient air or from additions of contaminants that contain oxygen or nitrogen.

Oxidation can cause rusting, corrode metal surfaces, generate acid formation, form sludge, varnish and increase viscosity. The rate at which these processes occur is highly dependent on the temperature of the oil. Most mineral oils will double the oxidation for each 18 degrees rise above 165 degrees. With the newer engines running hotter oxidation may occur more rapidly. Synthetic Oils are often required for high temperature engines as they are more stable than mineral oils. The synthetic oils are formulated with fewer impurities and compounds that are resistant to temperature related oxidation. Can you totally eliminate oxidation? Of course not. Have you ever noticed how long it takes for new oil spilled on the ground to turn dark? Oxidation is what causes the chemical reaction that creates this change and if the sun is shining down on the oil the process occurs quickly. You can however ensure the oil is maintained at the proper operating temperatures of your engine and ensuring the oil is flowing properly. Oil that has an extremely high viscosity has more body to the oil, flows slower and retains heat instead of dissipating the heat properly. It may also spend too much time flowing through sections of the engine with higher heat i.e. the turbocharger, raising oil temperature but this will not show up on any oil gage etc. You can also ensure that the oil levels are properly maintained if you run 2 gallons low you have removed 20% of the oil capacity placing an excessive strain on the remaining 80%. The oil will not have enough cool down time in pan before starting back through engine.

Oil analysis measures the oxidation of motor oil on an absorbance scale using infrared analysis to determine the level of oxidation present in the oil. This testing may be effected by water, glycol, soot, and fuel or in the case of synthetic oils Ester-based lubricants. It is not unusual for some new synthetic oils to show high oxidation levels based on the ester-based lubricants formulated into the oil. This does not mean that your oil will damage your engine as the ester-based lubricants are mimicking the oxidation on the infrared scale. Most labs will recommend oil changes or engine inspections when the oxidation level reaches 25 abs/cm however you should inquire as to the level of new oil for your brand before taking drastic costly actions. If your viscosity is not increasing and your total base number of your sample is within guidelines chances are the oxidation is not at a critical level.

Nitration usually indicates excessive blow-by from cylinder walls and rings or defects in the EGR system that is putting excessive amounts of nitric oxide into the oil. This nitration causes the creation of nitric acid when the water in the oil is heated and mixed with the nitric oxide. This acid will speed up the oxidation of the oil and increase viscosity while lowering the total base number. Sample results are similar to oxidation as they are reported on an absorbance scale with a limit of 25 abs/cm. The good news is the newer oils have been formulated to help reduce nitration and it is primarily a problem with natural gas engines. You can help to lower your nitration levels by keeping DPF’s clean eliminating back flow and properly maintaining your engine to eliminate blow-by.

Both oxidation and nitration levels can be kept low by removing contaminants from oil that contain oxygen and nitrogen i.e. water and soot and keeping the oil levels up to reduce excessive heat retention in oil.

Systems like the OPS EcoPur On-Board Oil Refiner that remove solid particles down to 3 microns will improve the oils ability to dissipate the heat and slow the oxidation levels. In addition by evaporating the water from the oil there is less acid formation, sludge buildup and oxidation.

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