Calculate Your Fuel Efficiency

Our desire for fuel efficiency has been around since the Model “T” however; there are several methods of evaluating fuel economy in the terms of (Miles Per Gallon) that are deceptive and not a true indicator of the progress made in developing more fuel-efficient vehicles as many salesman would like you to believe. Let us make true mileage simple to understand!

To understand true economy (Efficiency, or MPG) we need to evaluate how much energy it takes to move a given weight a given distance using MPG. The combination of a vehicle’s weight and its cargo is Gross Vehicle Weight (GVW). A loaded semi-truck gets about seven (7) MPG on diesel. To drive 100 miles at 7 MPG takes 14.28 gallons of fuel, or .1428 gallons per mile

1. Dividing the GVW 80,000 by 100 miles to get an equivalent, energy used to carry one mile. This gives us 800 lbs per mile.
2. Next, we need to figure out how much fuel it takes us to go one mile using our fuel mileage. To drive 100 miles at 7 MPG we divide 100 by 7MPG and it takes 14.28 gallons of fuel. Now we divide that number by 100 and get .1428 gallons per mile
3. Now we divide the 800 lbs per mile by .1428 gallons per mile and we find that the truck has moved 5602.24 lbs using only .1428 gallons of fuel. Or (19849 BTUs of heat energy) or
   each BTU of energy moved .283 lbs per mile

Diesel fuel contains 139,000 British Thermal Units (BTUs) of energy in each gallon; gasoline on the other hand has 125,000 BTUs in each gallon of unleaded fuel.

The 1949 “Pontiac Chieftain” with a Torpedo straight eight cylinder weighed 3500 lbs

1. Following the same formula, we start with the GVW or Vehicle Weight of 3500 lbs and divide it by 100 to get the lbs per mile figure. 35Lbs
2. The 1949 “Pontiac Chieftain” received better than 19 MPG or an equivalent used .05263 gallons per mile. When we divide gasoline’s 125,000 BTUs by .05263 we find that each mile it used the equivalent 6579 Btu’s heat energy.
3. Now we divide the 35 lbs per mile by 6579 Btu’s of energy and find
   each BTU of energy moved .0053 lbs per mile !

The 1990 Buick LeSabre 4 Door Sedan with a 3800 V6 engine weighing 3269 lbs

1. Following the same formula, we start with the GVW or Vehicle Weight of 3500 lbs and divide it by 100 to get the lbs per mile figure. 32.69 lbs
2. The 1990 Buick LeSabre received better than 25 MPG or an equivalent used .03125 gallons per mile. When we divide gasoline’s 125,000 BTUs by .03125 we find that each mile it used the equivalent 3906 Btu’s heat energy.
3. Now we divide the 32.69 lbs per mile by 3906 Btu’s of energy and find
   each Btu of energy moved .0084 lbs per mile !

The 2011 Smart Car 2 Door

1. Following the same formula again, we start with the GVW or Vehicle Weight of 1600 lbs and divide it by 100 to get the lbs per mile figure. 16 lbs
2. The 2011 Smart Car receives better than 35 MPG or an equivalent of .035 gallons used per mile. When we divide gasoline’s 125,000 BTUs of energy by .035 we find that each mile it used the equivalent 4375 Btu’s heat energy.
3. Now we divide the 16 lbs per mile by 4375 Btu’s of energy per mile we find
   each Btu of energy moves .0037 lbs per mile !

   
   This "Smart Car" moves only . 0037 Lbs per mile! Shure thay tell uou that it gets 40 MPG and it does, but, That is one of the worst rating of lbs moved per mile or uses of energy on the road since WW2, when cars were riding on Bias tires and driving on gravel roads in 1949?!

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References http://cogeneration.net/fuel-and-energy-conversion-and-equivalence/
1 Gal Gasoline (mid grade) 125,000 Btu’s
1 Gal of #2 Fuel Oil = 139,000 Btu’s