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Maintenance Section
Fuel Sulfur Content
The percentage of sulfur in the fuel will affect the
engine oil recommendations. Fuel sulfur is chemi-
cally changed during combustion to form both sul-
furous and sulfuric acid. These acids chemically
attack metal surfaces and cause corrosive wear.
Certain additives used in lubricating oils contain
alkaline compounds that are formulated to neutral-
ize these acids. The measure of this reserve alka-
linity in a lubricating oil is known as its Total Base
Number (TBN). TBN is essential to neutralize the
acids from combustion gases and to minimize cor-
rosive wear.
Any API classification performance oil should have
sufficient TBN for fuels with less than 0.5% sulfur.
For fuels with 0.5% to 1.5% sulfur by weight,
engine oil must have a TBN of 20 times the per-
centage of fuel sulfur as measured by the ASTM
(American Society of Testing Materials) D-2896
method. (ASTM D-2896 can normally be found at
your local technological society, library or college).
DAEWOO recommends infrared analysis (in con-
junction with wear metal analysis) of used oil in
determining the effectiveness of oil TBN and acid
neutralization.
For fuel with sulfur exceeding 1.5% by weight, use
an oil with a TBN of 30 and reduce the oil change
interval by one half. Also, infrared analysis and
wear metal analysis should be used to establish oil
change intervals.
Periodically request fuel sulfur content information
from your fuel supplier. Fuel sulfur content can
change with each bulk delivery.
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