Commercial Diesel Engine Oils
The performance of commercial diesel engine oils are
based on API categories. These API categories am
developed to provide commercial lubricants for a wide
variety of diesel engines that operate at various
If Caterpillar DEO (multi-grade) is not used, only use the
following commercial oils:
Preferred - API CG-4
Allowed - API CF-4
API CG-4 oils are preferred for use in Caterpillar engines
because of the fuel sulfur level. API CG-4 is the only oil
category that evaluates oils with engine tests utilizing
0.05 percent sulfur fuel.
The following explanations of these API categories can
be used to make the proper choice of a commercial oil.
CG-4 - CG-4 is the newest oil category. CG-4 oils were
primarily developed for diesel engines that are operating
with 0.05 percent sulfur diesel fuel. All of the laboratory
engine tests for this category were performed with 0.05
percent sulfur diesel fuel. CG-4 also defines oils that
have superior soot dispersancy. CG-4 oils will provide
improved viscosity control and improved crankcase
cleanliness in applications where oil soot is a problem.
CG-4 oils should also be used in engines that contain
hydraulically actuated fuel injection pumps; these are the
first oils to pass industry tests for foam control and
viscosity shear loss. CG-4 oils must also pass recently
developed tests for metals corrosion, and wear. CG-4
oils can be used in all Caterpillar engines where CF-4
oils are recommended.
CF-4 - CF-4 oils service a wide variety of modem diesel
engines. This oil classification was developed with 0.40
percent sulfur diesel fuel. The fuel used in the CF-4
tests represents the type of diesel fuels commonly
available world wide. CF-4 oils provide improved piston
deposit control and improved oil control when compared
to the CE category oils. CF-4 oils also provide improved
soot dispersancy compared to CD or CF category oils.
Some commercial oils meeting these API specifications
determined by close monitoring of oil condition and wear
metals. The Caterpillar SOS Analysis Program is the
preferred testing method.
Consult your Caterpillar dealer for the latest oil
Failure to follow these oil recommendations can
cause shortened engine life due to deposits and/or
Total Base Number (TBN) and Fuel Sulfur Levels For
Caterpillar Diesel Engines
Caterpillar Prechamber Combustion Engines
The TBN for a new oil is dependent on the sulfur level of
the fuel used. For precombustion chamber (PC) engines
running on distillate fuel, the minimum new oil TBN
(by ASTM D2896) must be 20 times the fuel sulfur level.
The minimum TBN of new oil is 5, regardless of low fuel
sulfur level. See the illustration.
Oil TBN shown by ASTM D2896 (Y). Percent of fuel sulfur by
weight (X). New oil TBN (1). Change oil when the used oil
TBN limit (2) is reached.