For any given percentage improvement
in mpg, the fuel savings percentage is less.

It's vitally important that you know
whether a given fuel economy measure
is expected to DECREASE your
fuel consumption or INCREASE
your miles per gallon.

Because of the way the mathematics work, it's vitally important that you know whether a given fuel economy measure is expected to DECREASE your fuel consumption or INCREASE your miles per gallon.

For example, about 18 percent increase in miles per gallon represents only about 15 percent savings in fuel. The bigger the numbers, the bigger the difference.

*The Fleet Manager's Guide to Fuel Economy, p.7.

Some sample mpg changes, the amount of fuel saved over one year
(assuming 100,000 miles traveled), and percentage changes.

Who benefits most?

Fleets with the most to gain from improving their fuel economy are the ones who use the most fuel.

If you use $1 million worth of fuel each year, and save just one percent, that's $10,000. If you use $100,000 worth of fuel, that same one percent saves you $1,000.

The good news is, the worse your fuel economy, the more you have to gain by improving it. For example, let's compare two fleets, one with relatively poor fuel economy (5 mpg) and one with relatively good fuel economy (7 mpg).

If both fleets make just a one percent improvement and run about 100,000 miles per year on each tractor, the fleet with the poorer fuel economy will save 200 gallons per year per tractor, while the one with better initial fuel economy will save 143 gallons per year per tractor.

So, if you use a lot of fuel and have relatively poor fuel economy, you have much to gain by improving it.