What are the key specifications for ultra-low sulfur diesel (ULSD)?

ULSD specifications: Sulfur - max 10-15 ppm (Euro V/VI, US). Cetane number - minimum 51 (Europe), 40 (US), higher is better ignition quality. Density - 820-845 kg/m3, affects energy content. Flash point - minimum 55C for safety. Viscosity - 2-4.5 cSt at 40C for injection system. Cloud point/CFPP - climate dependent, cold flow properties. Lubricity - HFRR <460 microns, may need additives. Aromatics - polycyclic aromatics limited for emissions. Stability - oxidation stability for storage. Achieving ULSD: deep hydrotreating at high severity, may require two-stage treating for difficult feeds. Specifications increasingly stringent - Euro 7 will add further restrictions on aromatic content and other properties affecting emissions.