Quote:
Originally Posted by Big Dave
The EPA does not test these trucks. I go by what people tell me.
My Ford (International engine) gets 24 on a bad day. No V-10 Ford gets over 12.
What's your answer about the VW? That's closer.
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The problem with going by anecdotes and other models is that there isn't enough data to come to any conclusion. Anecdotes don't wok for obvious reasons, and different manufacturers may not have gas/diesel engines in the same car with the same gearing and same displacement. For example, the 2011 jetta wagon has a FD of ~3.1 for the 2.5l gas engine while the diesel otoh has fds of ~2.8/~2.3 w/ a 2l engine. I imagine most of the difference in mileage is because the smaller diesels are geared much lower. If the gasser was geared proportionally lower than the diesel, or vice versa, then you could make a case that X engine is really A% more efficient than Y engine, but there's no way anyone could get a decent comparison on the epa combined w/o tweaking the transmissions. BSFC maps at least are objective.
It could be that the dodge gas engines have much worse BSFC than the cummins diesels, or it could be that they have comparable bsfc. Compared to gasoline engines in general, given the only data I've seen, it looks like cummins diesels have similar, albeit slightly better, BSFC. Unless large displacement gasoline engines have really poor BSFC, then I doubt there's going to much of an advantage (maybe ~10% or so) to a diesel swap. If you happen to have some BSFC data showing that the 4.7l/5.7l dodge V8 gassers are real pigs feel free to post it up.