Table of Contents
Advertisement
Definition of Properties of Engine Oil
Kinetic viscosity
Kinetic viscosity is a basic physical property of engine
oil and is considered as the most important aspect
when evaluating oil.
Contamination of oil due to blow-by gas and deteriora-
tion of oil or its natural aging increases the kinetic vis-
cosity and degrades the performance of viscosity,
which will cause the deposition of sludge inside the
engine and oil filter clogging. Contamination of oil due
to fuel and sheared molecules of viscosity index
improver in oil decrease the viscosity and degrade the
performance of viscosity, which will cause insufficient
lubrication and friction/wear of engine parts.
Base number
Base number shows the ability to neutralize acids
such as organic acid due to engine oil oxidation, or
sulfurous or sulfuric acid due to the sulfur content of
fuel.
Because base number indicates the amount of disper-
sant detergent in oil, it can be used to estimate con-
sumption of basic dispersant detergent. The ability to
disperse sludge declines as dispersant detergent is
consumed. So, the base number is often used as an
indication of cleaning capability decline.
Acid number
The acid number in oil increases as the organic acid is
being derived by the engine oil oxidation, or sulfurous
acid or sulfuric acid derived by the combustion of sul-
fur content of fuel, or the oil becomes contaminated
with imperfect combustion products.
An increase in the acid number will result in corrosion
or wear of the inner parts of the engine (such as cylin-
der liner and bearing) due to sulfur content, and the
piston ring seizure due to sludge.
Water content
Water in oil promotes corrosion/wear, and decreases
lubricity in sliding parts.
Flash point
The flash point is lowered by contamination with fuels.
Flash point is used to check the fuel dilution of oil. The
dilution of oil reduces oil film, and causes insufficient
lubrication that will cause friction or wear of engine
parts.
Insolubles
Insolubles include acid products of engine oil, imper-
fect combustion products, sludge or soot, worn metal
particles and dust. Insoluble is an indication of degra-
dation/contamination of oil.
Dispersant detergent, which is an additive in engine
oil, absorbs sludge particles, and disperses them as
fine particles in oil. Total insoluble density and remain-
ing dispersibility can be obtained by measuring insolu-
ble and coagulated insoluble (chemical specialties
which stop action of disperse detergent and collect the
sludge dispersed in oil) to understand the engine oil
contamination level, and thereby, the insoluble value
can be a marker to prevent the piston ring from sei-
zure or premature wear.
Chapter 5 ENGINE OIL
5-5
Advertisement
Table of Contents
Troubleshooting
