No one has mentioned Cetane Value yet.
Just like gasoline has a octane
diesel has a cetane value, the higher the cetane value the lower the temp an
engine can start, less
diesel combustion knock occurs, less
engine deposits occur less smoke fumes and
odor.
The cetane number an indication of the types of hydrocarbon in the
fuel more parafinnic, less napthalenes, and aromatics.
Depending on the crude blend and the refinery, virgin stocks (ie not catalytically cracked to smaller molecules) will produce the highest cetane number, but will also have the highest pour point (temperature at which the diesel gels).
All diesel at the
pump will meet the high speed diesel engine specifications, there are many other grades of diesels (not at pumps)
sold for large engines.
So for
marine use don't buy
winter diesel (if possible), if you
purchase some poor quality diesel in the third world, do not operate your engine at full
power, warm it up well, install new filters, cool it down well, consider adding a cetane improver.