Trucks at Work
The forgotten fuel economy factor

The forgotten fuel economy factor

The two main issues with fuel economy are idle time and how you drive the truck. Those are management issues, not engine design issues.” –Tom Diefenbacker, director of diagnostics, electronic features, support for Navistar and former director of electronic products for Detroit Diesel Corp.

It’s funny, in a way: so much of the truck fuel economy discussion emanating from any number of corners in government these days is focused almost solely on the hardware involved, yet ignores what’s likely the single most important factor in reducing fuel consumption: the skill of the driver behind the wheel.


I touched on the subject of drivers in this space earlier this week, but it still just amazes me how much driver behavior gets overlooked by folks outside the trucking business.

The quotation from Tom Diefenbacker above sums it all up pretty neatly, I think – and those words are over seven years old now, uttered right as the industry began its long government-mandated emissions journey to remove particulates, oxides of nitrogen, and other pollutants from truck exhaust.

Countless truck engineers from all the major OEMs – engine and truck makers alike – have told me (and continue to tell me) that all the design improvements they make to improve heavy truck fuel economy can be nullified simply by poor driving and operating habits: excessive engine idling, improper shifting, excessive road speed, hard braking and accelerating … the list goes on.

Yet it’s also not easy to drive a truck to maximize fuel efficiency, either. Just watch as Detroit Diesel’s one-and-only Chuck Blake provides some fuel efficiency tips to drivers below. Note that drivers really need to pay attention to what they’re doing to operate their vehicle in its fuel sipping “sweet spot” over the course of different road conditions.

[And also note that this video was produced for the now long-departed Sterling Trucks.]

Now, sure, many of the government’s fuel economy experts rightly note that using automatic or automated transmission to make all the proper shifts for the driver can keep a vehicle in its best fuel-economy mode while driving.

But that ignores the fact that most heavy trucks today are still spec’d with manuals, with fleets largely favoring 10- and 13-speed models, while others (largely owner-operators but some fleets as well) stick with 18-speed monsters.

Do you think it’s easy to stay in the proper gear to maximize fuel economy with a manual? I sure don’t. It’s a skill acquired after years of experience – I know because I’ve talked to the men and women who spent careers gaining said experience.

[Just watch as an Eaton engineer explains how to properly shift both a 13- and 18-speed transmission. You sure don’t learn how to do that in just a couple of hours with a trainer!]

Finally, it’s also important to note some design differences that affect the “driving style” for the diesel engine brands and models in the market today.

The old saying that “no two drivers are alike” can also be applied to diesel engines as well, for each make and model comes with their own specific fuel map, horsepower ratings, peak torque and rpm [revolutions per minute] points, and operating characteristics, just to name a few.

Knowing how to drive one type of engine to obtain ideal fuel economy doesn’t automatically mean a driver can perform the same feat with a different model.

[For instance, watch this video from Navistar concerning driving tips for its MaxxForce diesel engine line. Note that a 5 minute warm up is needed for these engines. But if you recall the old Sterling video at the top of this post, Detroit Diesel models did NOT require a 5 minute warm up: a small difference, yes, yet it’s one that adds up in terms of fuel economy and engine health over time.]

A final note: research by Schneider National indicates that fuel economy and safety are interrelated when it comes to drivers

Two years ago in a Fleet Owner webinar, Don Osterberg, Schneider’s vice president of safety, driver training, and security, stressed that there’s a strong the correlation between fuel-efficient driving and safe driving.

“If you are wondering why the safety person is talking about MPG (miles per gallon), based upon our analysis, our best drivers for MPG are also our safest drivers,” he noted.

In a study, Schneider’s top 100 drivers in terms of MPG had a 37% lower accident rate than the 100 drivers with the lowest MPG, he pointed out, while the top 500 MPG drivers had a 23% lower accident rate and the top 1,000 MPG drivers had a 21% lower accident rate than the lowest 1,000 MPG drivers.

Those are some pretty striking numbers – illustrating that, wherever we go in terms of heavy truck fuel economy mandates, the driver must remain a key part of the calculation.