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Used Oil Analysis
programs for engine oils, such as Petro-Canada's
"LUBRI-TEST" provide several customer benefits:
- Reduce unscheduled
vehicle downtime
- Improve vehicle
reliability
- Help organize
effective maintenance schedules
- Extend engine life
- Optimize oil change
intervals
- Reduce cost of
vehicle maintenance
Used engine oil analyses
are carried out principally to determine the overall
condition of an oil. 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
- 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 sytems, 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 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.
- Insolubles -
suspended material present in the oil, due to
presence of soot from diesel fuel combustion and
contamination from airborne dust, dirt or sand.
- Total 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.
- Total Base
Number - measures the reserve alkalinity of
an oil, which is the ability of an alkali to
neutralize the effect of acid formation.
- Wear or Additive
Metals - The presence of the following
elements is usually looked for by Inductively
Coupled Plasma Emission Spectroscopy: Aluminum,
Barium, Boron, Calcium, Chromium, Copper, Iron,
Magnesium, Phosphorus, Sodium, Tin and Zinc.
Used Oil Analysis Tests
| Test |
Warning
Limit |
| Viscosity |
|
cSt @ 40°C
|
25% change
versus the new oil viscosity |
cSt @ 100°C
|
15% change
versus the new oil viscosity |
| Coolant |
Any positive
identification |
| Water |
Greater than
0.1% |
| Dilution |
Greater than 5% |
| Insolubles |
0.5% or more |
| Total
Acid Number |
More than 5.0
units |
| Total
Base Number |
No lower than
3.0 to 4.0 units |
| Element |
Warning Limits |
Comments |
| Iron (Fe) |
Greater than 100 ppm |
High levels indicate worn
crankshafts, valves, cylinder-liners, bearings |
| 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 and bushings |
| 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
anti-freeze 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 |
Magnesium (Mg), Calcium
(Ca),
Barium (Ba), Sodium (Na),
Phosphorus (P), Zinc (Zn) |
These elements may be
part of the additive package. They remain in the
oil and do not deplete. |
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