Quote:
Originally Posted by Big Dave
Props to Diesel Dave for exemplary performance.
Much of it is due to his recognition of the importance of road speed in the road load equation.
Aero drag HP goes up with the cube of road speed.
Everything else is proportional to road speed.
Few people (me included) can keep their speed down like DD.
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The numbers are based on a commute. A defined course. That is the larger context. While the average speed is part of it, it isn't as though this truck is being used for all sorts of errands and road trips. It would be inaccurate --
a misrepresentation -- to say that, "well, there's this Dodge guy running all miles at 30-mph getting X-mpg", as the use is within a defined set of parameters.
Put another vehicle making the same type of drive which is the daily work commute -- with notes to vehicle spec, climate & terrain --
then one might be able to make comparisons based on average speed.
This is not a one-off stunt with controlled conditions as with a test track and a team of drivers running 24/7 to hit 2k miles in a couple of days. Nor is it a truck used in commercial service running 200-miles from base and back to hit 2k miles in a week or so. Etc. Average speed means different things in both those tests if only for the number of acceleration and braking events.
And this "test" by
DD is run daily -- summer, winter, fall and spring -- and is what elevates it beyond the above types: an ordinary guy doing an extraordinary thing. Great physical and mental discipline . . and by no means beyond the rest of us, even if our numbers don't hit this lottery-winning series.
One might say that -- with discipline in the daily grind -- one can underwrite extended vacation travel: "we're going to visit Aunt Sarah and take the kids to the Everglades and
the fuel is free" based on an annual fuel budget.
Or extract the maximum miles from a particular vehicle over a given lifepan.
But if we change the commute of
DD to one of a different mix of roads and distances, and throw in a climate or terrain change, while there will have been an impressive percentage increase over EPA (derived) the absolute numbers based on a given average speed won't be the same.
The average speed is not the gateway to understanding this demonstration.
If one wants to simplify this for others, then saying that
DD cut his work commute bill by 75% would be better. And since GM or Ford diesel truck owners won't accomplish the absolute numerical change,
the percentage change is the thing to emphasize. As in, "want to pull the fifth wheel travel trailer 2000-miles for free this summer . . . ?
.