Dollars & Sense

Kevin Rutherford

How to do a fuel-saving test

Kevin Rutherford | January 01, 2012

For more than 15 years I’ve been testing devices and strategies intended to improve fuel mileage. Though it can be labor-intensive, developing your own testing methods pays off.

If you plan well, control as many variables as possible, and keep accurate, detailed notes, you’ll save a lot of money and gain invaluable knowledge about your operation. There are many products to evaluate, such as wide single tires, aerodynamic add-ons and limited highway speed to 55 mph.

1. DETERMINE THE POTENTIAL FOR IMPROVEMENT. No matter what I’m considering, I start with the step I wrote about last month. That is, I determine if the product could improve the efficiency in any of the four areas that contribute most to fuel economy – aerodynamic drag, rolling resistance, mechanical resistance and engine thermal efficiency.

2. IDENTIFY THE KEY VARIABLES. One key part of fuel mileage testing is making sure you’re tracking fuel mileage accurately and consistently. Understand all of the variables that affect fuel economy, such as speed, weight, terrain, weather, fuel quality, road surface, traffic, idle time and mechanical conditions. I’ve identified more than 40 such variables.

Visit for Rutherford’s online tutorial that walks you through the process of keeping fuel mileage records and detailed notes for testing. You’ll also find resources for controlling fuel mileage variables, which is critical when testing fuel-saving devices.

3. SET A 30-DAY CONTROL PERIOD. I always run 60-day tests. I use a 30-day control, or baseline, prior to testing the device or strategy. This means I track the fuel mileage closely on the test truck for 30 days prior to the change and make sure that everything is consistent. If during the 30 days, for example, I developed a leaking charge air cooler, I would repair or replace it, then restart start the 30 days.

4. TEST THE DEVICE. Once I have a consistent 30-day timeframe of fuel mileage results, I add whatever device I’m testing. I track fuel mileage closely for the next 30 days. Once that data is complete, I compare it with the results from the control truck.

As with the first truck, be sure that nothing major changes during the actual test. For example, try to ensure you won’t need to replace tires during the testing procedure since new tires have much more rolling resistance.

In certain parts of the country, early winter testing wouldn’t be a good idea. Weather conditions could change drastically from the control test period. Fuel quality is changing as well due to winter blend fuels.

I have three trucks that run dedicated, so I’m able to control some of the major variables by testing with two vehicles. They run the same lane every day, most days within minutes of each other. I use the same strict control standards on the second truck, the difference being I don’t make any changes to that vehicle during the 60 days. That helps me account for some of the variables I can’t control, such as weather and traffic.

This testing procedure is intensive and time-consuming. But because I’ve stuck with it over the years, it’s allowed me to develop a deep understanding of what affects fuel economy and, most importantly, how to improve it.

Kevin Rutherford is an accountant, small-fleet owner and the host of “Trucking Business & Beyond,” which airs on Sirius XM Radio’s Road Dog Trucking Radio. Contact Rutherford through his website,

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