The cetane number is so high as to be irrelevant. It is good that it is high, but above a certain level there is no improvement in performance.
re the 25% improvement in efficiency, this may apply to older engines with mechanical fuel pumps - the cetane no. would probably be more relevant here, as you could retard the timing with the quicker burning. For modern common-rail injectors, which nearly all car 4WD and many truck engines now use, the increase seems nearer 2%: see this more analytical test from Mercedes, rather than a "we drove across a desert and saved 25%" comment.
As a comparison, if my Patrol (2.4 tonnes) was to achieve a 25% fuel saving on GTL Diesel, it would be using 7.5l/100km, or 38mpg. While I would be very happy with that, it is putting the efficiency of the engine at about 60%, which is probably impossible. That is more economical than the original Mini, but with better performance.
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