#2 diesel fuel is pretty crude fuel by modern standards -- nothing at all like Jet A (or B, if you can find it!). It is usually simply the middle fraction of crude oil -- the gasoline and some of the just heavier than gasoline components are distilled off, and the tar is left behind. Everything else is #2. Pour points can be pretty high (as anyone who has had their fuel gel can testify), although good stuff has a pour point as low as -30F.

The sulfur is there in complex organic molecules, and has a number of effects -- first and foremost, these compounds tend to provide a large amount of the lubricating qualities of the diesel fuel. Second, the presence of sulfur seems to catalyze combustion, especially uuder high load conditions, and reduce both injector knock and soot formation. These are all good things.

The bads things are emissions of sulfates and other particulates, usually "breathable" -- meaning the particles are small enough to go right down your lungs and stay there), some SO3 is emitted (sulfuric acid -- one of the nasties in acid rain), and I think the production of metal sulfides rather than metal oxides -- the sulfides are more of an environmental problem.

#1 diesel is both more volatile (burns better) and has considerably less heavy end material, so produced less soot from incomplete combustion. Takes more of it to give the same power, though -- less BTU/lb.

I personally suspect the answer is oxygenated fuel (biofuels -- plant or animal fats/oils) to reduce the soot and enhance cleaner combustion over all. Biofuels may also produce less aromatic residue (benzene and substituted benzenes), all of which are bad guys.

Diesel fuel in the US isn't a high quality product, lots of room for improvement there.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!