voiding the warranty doubtful, but not unheard of. i do not have my EcoDiesel owners manual but i do not remember any warnings as to your question, Gball.
there may be more to it by searching the web i pulled this from opti-lube's web site:
The Importance Of Cetane
Diesel engines will operate fine on any cetane rating between 40 to 55, but the higher the number, the shorter the ignition delay is, and the more complete and efficient the combustion cycle becomes. In our research we found that cetane numbers in ULSD fluctuate between 40 to 45. And coinciding with what we've seen, with inconsistencies in cetane ratings at the pump, many diesel owners experience fluctuating fuel mileage.
During the refinement of ULSD, fuel is flooded with hydrogen to remove sulfur, but in the process also removes much of the fuel's lubrication properties, as well as cetane content. This leads to many things, but we're focusing on the fact that cetane numbers aren't consistent. This means each time you fill up at your local station, the quality of fuel is different. Knowing this, we contacted FPPF about using its 8+ Cetane Improver.
The Importance Of Lubricity
Another reason ULSD has been blamed for premature fuel system and engine wear is due to its low sulfur content. At 15 ppm (out of 1 million parts, just 15 can be sulfur), ULSD contains only a fraction of the sulfur concentration found in the previously used low-sulfur diesel (LSD), which was roughly 500 ppm. And since sulfur acts as a lubrication agent in diesel fuel, ultra-low sulfur content in ULSD is thought to be one of the main suspects in causing fuel-related problems in pre-2007 diesels, which were designed to run primarily on LSD.