On Mon, 21 Nov 2011 19:10:55 -0500, John H
wrote:

It is a wonder how a 6.6 liter diesel can get better mileage than a 5.6 liter gasser, but they do.

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There's no magic to it, just the laws of physics. Diesel fuel has
more BTUs per gallon and diesel engines operate at a much higher
compression ratio. In addition a diesel engine does not operate
against the constriction of a throttle plate. The rule of thumb is
that a diesel engine will burn about 1 gallon per hour for every 17 or
18 horsepower. A gas engine burns 1 gallon per hour for every 10 hp.