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You have to keep in mind a couple of things about the fuel mileage on these 08's. One, you are feeding more horses that you did in prior year models. My 08 is 350 hp vs 325 hp in my 07 & 05 & 04 6.0's. Just takes more fuel. My mileage is off as is everyones. Another reason is the emission level requirements this engine meets. In order to meet these EPA requirements, the engine utilizes passive and active regeneration cycles. Same as in big bore engines. Simply put, the ECM moniters your driving. If heat does not reach a certain level to burn off the soot through passive regeneration, the ECM commands the injectors to inject a predetermined amount of fuel into the exhaust cycle in order to burn off the soot in the DPF. This is why your engine RPM suddenly raises to about 11-1200 or so when you are sitting at a light with your mind off in space and it gets your attention. You have entered an active cycle. If you drive a lot of highway at 50+ MPH, you will do most of your regeneration in the passive cycle because of the heat generated. City driving is another thing altogether. As with refuse trucks that go house to house, they don't reach high enough heat levels to allow passive regeneration. For that reason we set them to an active mode at about 25 MPH.
The amount of fuel used in this cycle is being reviewed. It would not surprise me to see this adjusted in the future by way of a re-flash as it is controlled by the ECM. Fuel mileage on this engine (6.4) in reality should be better than what we got on the 6.0.
[/ QUOTE ] Question,if your slowing for a light and it's icy,how are you going to get it stopped,put it in nutural,we used to do that back in Illinois to get the toqure off the back drive tire's or the front tire's would slide and we'ed go right past the stop sign,and that was at 550-600 rpm,not 1200 rpm,look at the toqure you get at 1200 rpm,my truck and 5th wheel will start moving at that rpm,and that's over 20,000 #'s!!