According to a table on the effects of fuel properties on engine performance in a published diesel engine manual (3rd edition), increasing the cetane number affects the engine in the following ways:

1. Starting Improves
2. Lubrication Improves (presumably injection components, not engine)
3. Smoke Decreases
4. Exhaust odor Decreases
5. Power output not affected
6. It says fuel consumption is related, presumably decreases as cetane increases, as per your results.
7. Increases combustion chamber deposits.

So, basically, it gives you a great deal of advantages but the tradeoff is more combustion chamber fouling.

__________________
"I would rather be ashes than dust!
I would rather that my spark should burn out in a brillaint blaze
than it should be stifled by dryrot.
I would rather be a superb meteor,
every atom of me in magnificent glow,
than a sleepy and permanent planet.
The proper function of man is to live, not to exist.
I shall not waste my days in trying to prolong them.
I shall use my time."

-Jack London 1876-1916

1983 300CDT (running WVO since 12/05)
1981 300SD (parts car)