I personally have no clue what the difference is between the two. I just checked stanadynes website and WOW they have alot of information and tell you exactly what additive you need. They have 3 pages of information and explain what the differences between the two. Ill be studying this real soon.
http://www.stanadyne.com/new/index.asp Under additives then diesel fuel update Ultra Low Sulfur Diesel
Beginning in 2006 diesel fuel for on-highway
use must have no more than 15 parts per
million sulfur. This is a
97% reduction from the
previous limit of 500 ppm. Sulfur is removed
from diesel fuel at the refinery by a
process
called hydro-treating which also affects the
fuel in other ways. The American Society for
Testing and Materials (
ASTM) publishes the
standard for mineral diesel fuel—
ASTM D975
which the refineries comply with.
Advantages of ULSD
+
Reduced exhaust emissions
+
Improved cold startability and reduced white
smoke at cold startup
Disadvantages of ULSD-
Higher Cost
-
Lower energy content. Less BTU’s per
gallon means reduced power and fuel
economy
-
Possible premature fuel system wear. The
process of removing sulfur can also reduce the
natural lubricity of the fuel. There is now a
lubricity specification in the D975 standard but
it is not as high as what the fuel system
manufacturers recommend.
-
Compromised fuel stability. ULSD tends to
be less stable and will deteriorate sooner than
the previous diesel spec.
-
Fuel System leaks. Reducing sulfur also
reduces aromatics. This can result in rubber
seals an hoses in some fuel system
components shrinking and resulting in fuel
leaks. NOTE: Stanadyne fuel systems do not
use natural rubber seals but use Viton®
seals
instead