valve and mix with the intake charge. The DPF traps soot and particulates from the exhaust and virtually eliminates the black smoke that most diesel engines expel upon acceleration. The engine computer is programmed to periodically inject extra fuel in the exhaust stroke of the engine (which is called a DPF Regen or regeneration) to burn off soot that accumulates in the DPF. This engine is designed to only run on ultra low sulfur diesel (ULSD) fuel which has no more than 15 ppm sulfur content; using regular diesel fuel results in emission equipment malfunctions and violates manufacturer warranties. The 6.4L has had one recall (safety product recall 07S49 was released on March 23, 2007) that addresses the potential for flames to come from the tailpipe of the truck. This problem arises from the DPF which is part of the diesel after-treatment system. A PCM recalibration was released to eliminate the possibility of excessive exhaust temperatures combined with certain rare conditions resulting from what is becoming known as a "thermal event". Key specifications Fuel injection system: High pressure common rail Valve train: OHV 4-valve Compound VGT turbo DPF Advanced multi-shot piezoelectric fuel injection control Common issues Piston ring failures in #7 and #8 cylinders due to regeneration process. During regeneration, fuel is injected during the exhaust stroke in order to increase the exhaust temperature for DPF cleaning. This exposes the piston rings to excessive heat which eventually causes the piston rings to lose tension, causing low to no compression (compression skip) and excessive blow-by. Rocker arm tips impacting (especially on lower geared trucks) due to higher pressure on valve-train (that was not upgraded from the 6.0 liter engine design) after . Turbo-charger bearing seal failures (which in turn allows engine lubricating oil to leak past the bearing seal) due to regeneration process pushing high exhaust temperatures thru the turbo-charger. This condition will precipitate premature clogging of the DPF, which then causes the engine to stay in regeneration mode. If this condition is not corrected quickly, the leaking seal will eventually allow all the engine oil to be pumped out of the engine through the exhaust, causing complete engine failure due to lack of lubrication. Higher incidents of cavitation erosion of the front cover due to the larger water pump impeller speed, causing coolant to leak into engine oil. EGR cooler failures allowing engine coolant to flow back into #8 cylinder