## Tuesday, October 7, 2014

### Calculating fleet average fuel efficiency

Calculating fleet average fuel efficiency

Question:   Below are the sales numbers and my rough estimate of the fuel efficiency for the top twenty selling vehicles in August 2014.   What is the fleet fuel efficiency for vehicles sold in August 2014?

 Sales estimates and fuel efficiency estimates August 2014 Aug-14 Fuel Efficiency Ford F - Series PU 59,863 22 Chevrolet Silverado PU 50,176 22 Dodge Ram PU 36,612 22 Honda Accord 32,956 34 Toyota Camry 28,507 35 Honda CR-V 23,722 31 Toyota RAV4 22,724 29 Honda Civic 22,263 36 Ford Escape 21,718 30 Ford Fusion 21,693 36 Nissan Altima 21,675 33 Toyota Corolla / Matrix 20,530 30 Hyundai Elantra 18,848 38 Chevrolet Cruze 18,415 38 Chevrolet Equinox 17,266 24 Nissan Rogue 17,229 30 GMC Sierra PU 16,763 22 Ford Explorer 15,795 23 Ford Focus 15,397 36 Chevrolet Malibu 15,186 34

Answer:   The fleet fuel efficiency is calculated with a harmonic average.   It is the ratio of the sum of total sales to the sum of the sales to fuel efficiency ratio of each vehicle.

From the table below observe that total sales in the month of August 2014 is 497,388 vehicles.   The value of the vehicle sales to fuel efficiency ratio for the 20 vehicles is presented in the far right column of the table below.   The sum of these ratios is 17,882.

The fleet fuel efficiency is 497,338/17,882 or 27.8.

 Calculation of Fleet Fuel Efficiency for August 2014 Sales Aug-14 Fuel Efficiency Ford F - Series PU 59,863 22 2,721 Chevrolet Silverado PU 50,176 22 2,281 Dodge Ram PU 36,612 22 1,664 Honda Accord 32,956 34 969 Toyota Camry 28,507 35 814 Honda CR-V 23,722 31 765 Toyota RAV4 22,724 29 784 Honda Civic 22,263 36 618 Ford Escape 21,718 30 724 Ford Fusion 21,693 36 603 Nissan Altima 21,675 33 657 Toyota Corolla / Matrix 20,530 30 684 Hyundai Elantra 18,848 38 496 Chevrolet Cruze 18,415 38 485 Chevrolet Equinox 17,266 24 719 Nissan Rogue 17,229 30 574 GMC Sierra PU 16,763 22 762 Ford Explorer 15,795 23 687 Ford Focus 15,397 36 428 Chevrolet Malibu 15,186 34 447 Total 497,338 17,882

Caveats:  This estimate may be off, possibly far so.    There are many types of each model and each version of each model has its own fuel efficiency number.  The fuel efficiency estimates used above are quick estimates of the median for each model.

The EPA has reported recent improvements in fuel efficiency.

This is good news but it is my understanding that corporate average fuel efficiency numbers are based on sales projections.

In the best of worlds I would be able to crunch statistics to confirm the EPA result.   But the EPA’s job is really data intensive and I don’t have access to this type of detailed information.

Also, the EPA gives vehicle fuel efficiency of 100 mpg for any car that can use alternative fuel.    I do not know the impact of this rule on reported numbers.   I do know that this rule allows firms to produce more low fuel efficiency cars than they otherwise would be allowed to.