MPG, or miles per gallon is a traditional means of measuring fuel efficiency of cars and this extends to the measurement for environmentally friendly eco green cars. MPG is currently deemed the defacto reference for car fuel efficiency measurement.

In Europe, mileage figures are given in liters per kilometers instead. In US, official MPG numbers of various car models are published and used for reference as consideration benchmark for car purchases. Of course one would consider other criteria such as interior spaciousness, comfort and feel, power, etc.

The hottest debate currently in fuel efficiency is the effectiveness of the relative measurement of MPG. Does MPG or miles per gallon give a good perspective to the real efficiency in comparison to other vehicles? That is, in a replacement scenario, reversing the formula to measure GPM or gallons per mile would make more sense.

The rationale of GPM or gallon per mile is especially helpful. 2 professors in Duke University reiterated the significance of this formula especially in “trade-off” situations in the following example.

The GPM, gallons per 100 miles formula is particularly useful for car shoppers looking for replacement vehicles or comparing fuel performance between two vehicles. To help you visualize the formula in greater perspective, there are two parts to the following rationale:

  1. Convert the formula from MPG to GPM
  2. Convert the comparative gallon unit difference into Cost Savings

For example, most people ranked an improvement from 35 to 50 mpg as saving more gas over 10,000 miles than an improvement from 18 to 28 mpg, even though the latter saves twice as much gas.

Now take the measure of fuel efficiency expressed in gallons used per 100 miles rather than mpg. From this perspective, 35 mpg becomes 2.8 gallons per 100 miles and 50 mpg is 2 gallons per 100 miles. 18 mpg becomes 5.5 gallons per 100 miles, and 28 mpg is 3.6 gallons per 100 miles. Convert this to today’s fuel cost and you would know that the latter is a better choice.

Especially in situations when replacing a vehicle, the greatest cost savings in fuel efficiency is Not in choosing the higher MPG but in choosing the Greater Difference in GPM between the old and the new choice.

And in addition, note that the Greater cost savings in families with more than one vehicle, is the improvement of the fuel efficiency of the less efficient one.

So the next time before you decide to buy any car, and if fuel efficiency is your major concern, remember to do that quick conversion calculation.

Yes, you can have your cake and eat it too. Think smart!

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