Normals pentane
insolubles are the insoluble matter
which can be separated from a solution of oil in n-pentane and in addition
to benzene insolubles, may include
insoluble resinous bitumens
produced from the oxidation of oil. While
this
test was designed
primarily for use with used
engine oils, it does have some
value in determining that a breakdown has occurred in gear
oils. Any appreciable amount
of pentane insolubles in used
gear lubricants indicates
that the
gear box has been
quite hot, usually above 300
degree F.
Benzene insolubles
are that portion of n-pentane insolubles
not soluble in benzene and may
include insoluble matter
produced by oxidation and thermal
decomposition of the oil
and oil additives. Any suspended
particles from metal
wear or from external
contamination will also be
present in the benzene insoluble fraction.
