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Old 09-26-2012, 09:33 PM   #4 (permalink)
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Join Date: May 2011
Location: Indiana
Posts: 1,194

White Whale - '07 Dodge Ram 2500 ST Quad Cab 2wd, short bed
Team Cummins
90 day: 37.68 mpg (US)
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Yes, assuming your goal is economical, then you need to compare cost improvement (cents/mile). This will include the cost of diesel + the cost of the LPG. If you wish you could calculate an "equivalent fuel economy" on a cost basis like this:


M = miles travelled
Gd=gallons of diesel used
C= cost ratio of LPG to diesel, e.g. (price of LNG per gallon/price of diesel per gallon)
Gl=gallons of LNG used

That way if the cost per gal for LNG is half that of diesel it "counts" as half a gallon of diesel.

If you objective is technical equivalence, then you'll have to do something similar with energy content instead of price. If your objective is carbon dioxide related that you can weight it by the carbon content.
Diesel Dave

My version of energy storage is called "momentum".
My version of regenerative braking is called "bump starting".

1 Year Avg (Every Mile Traveled) = 47.8 mpg

BEST TANK: 2,009.6 mi on 35 gal (57.42 mpg):

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