Used Oil Analysis

Used oil analysis programs for engine oils, such as the 360 Technical Expertise Oil Diagnostics program, provides several customer benefits:

  • Reduce unscheduled vehicle downtime

  • Improve vehicle reliability

  • Help organize effective maintenance schedules

  • Extend engine life

  • Forecast extended oil change intervals

  • Reduce cost of vehicle maintenance

Used engine oil analyses are carried out principally to determine the overall condition of the oil and the engine. Monitoring an oil’s condition at successive intervals, over a relatively long time period, can be used to establish:

  • Presence of Undesirable Contaminants, such as:

    • –  Excess Wear Metals

    • –  Gasoline or Diesel Fuel

    • –  Coolant and excess water

    • –  Road Salt

    • –  Dirt, Sand or Dust

  • Optimum Oil Change Interval

The following items are tested to determine the condition of an engine oil:

  • Viscosity - is the measure of an oil’s resistance to flow. An oil can “thicken-up” due to oxidation, the presence of contaminants, or evaporation of light components. It can “thin-down” due to oil shearing or fuel dilution.
    Reported as cSt @ 40 C and cSt @ 100 C.

  • Coolant - ethylene glycol is the major component of antifreeze coolant systems, so the presence of glycol is determined. A positive test result indicates a defective gasket or a cracked head/block. Detection of glycol requires immediate attention, as it reacts quickly in a hot engine to become acidic and form varnish and sludge.

  • Water - presence due to condensation from low temperature engine operation or from a leak in the cooling system.

  • Dilution - the amount of gasoline or diesel present in an oil.

  • Acid Number - expresses the quantity of base required to neutralize all the acidic constituents present in the oil. Often an indicator of how oxidized an oil has become.

  • Base Number - measures the reserve alkalinity of an oil, which is the ability of an alkali to neutralize the effect of acid formation.

  • Wear Metals or Additive Elements - The presence of the following elements is usually determined by Inductively Coupled Plasma Emission Spectroscopy: Aluminum, Barium, Boron, Calcium, Chromium, Copper, Iron, Magnesium, Molybdenum, Phosphorus, Sodium, Tin and Zinc.

  • Degradation by-product - includes oxidation, nitration and sulphation as determined by the FTIR method. Elevated results, above normal trends, generally indicate excessive stress of the oil due to extended oil service or other combustion related issues.

  • Soot - The fine black particles, chiefly composed of carbon, produced by incomplete combustion of the fuel.


Viscosity, cSt @ 40°C 25% change versus the new oil viscosity
Viscosity, cSt @ 100°C 15% change versus the new oil viscosity
Coolant Any positive identification
Water Greater than 0.1%
Fuel Dilution Greater than 5%
Acid Number More than 5 units (engine oil) or 1 unit (industrial oil)
Base Number No lower than 3 to 4 units
Soot Greater than 5%*
Oxidation Greater than 30 A/cm (above baseline)

* Confirm OEM recommended limits

Iron (Fe) Greater than 100 ppm High levels indicate worn valves, cylinder-liner, bearings, crankshafts.
Chromium (Cr) Greater than 10 ppm High levels indicate worn piston rings, bearings or contamination by antifreeze.
Copper (Cu) Greater than 20 ppm High levels indicate worn bearings and bushings.
Tin (Sn) Greater than 10 ppm High levels indicate worn bearings, bushings and oil cooler leeching.
Aluminum (Al) Greater than 20 ppm (>80 ppm Aluminum Block Engines) High levels indicate worn pistons or engine block.
Lead (Pb) Greater than 25 ppm High levels indicate worn bearings. Where leaded gasoline used, results are meaningless.
Boron (B) Greater than 20 ppm High levels indicate radiator fluid leak. Some engine oils contain a boron dispersant additive. Check sample of new oil.
Silicon (Si) Greater than 20 ppm High levels indicate presence of dust or sand. May also be due to high level of silicone anti-foam. Check sample of new oil. Radiator fluids contain silicates that show up as Silicon in sample.
Magnesium (Mg), Molybdenum (Mo), Calcium (Ca), Barium (Ba), Sodium (Na), Phosphorus (P), Zinc (Zn), Potassium (K) - These elements may be part of the additive package. They remain in the oil and do not deplete. The presence of Na and K can indicate a leak of radiator fluid.

ppm = parts per million


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