5-6
Chapter 5 ENGINE OIL
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 dilution of fuel. The
dilution of fuel reduces oil film, and causes insufficient
lubrication that will cause friction or wear of engine
parts.
Insoluble
Insoluble include acid products of engine oil, imperfect
combustion products, sludge or soot, metal abrasive
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 engine oil con-
tamination level, and thereby, piston ring seizure or
premature wear can be prevented before it occurs.