Wide base single tires save fuel.
Michelin Wide base single tires save fuel.

When the EPA got diesel engine exhaust emissions about as low as it could, it set out to find new ways to reduce air pollution and slow the effects of climate change.

It did it in three stages, starting in October 2002 (in advance of 2004 regulations) with a lowering of allowable nitrogen oxides (NOx). In 2007, it limited particulate matter (PM) by mandating diesel particulate filters (DPF). PM is soot, ash, and unburned hydrocarbons. In 2010, EPA further reduced NOx and PM to levels impossible to measure only a decade earlier. We now have the cleanest burning on-highway diesel engines in the world.

Emissions measurements are made in grams of pollutant per horsepower produced per hour (g/hp/hr). Until now, only PM and NOx were considered. But the greenhouse gas considered the greatest contributor to climate change, carbon dioxide (CO2), was omitted from the calculations.

The newest requirements, called GHG 2014, involves CO2 and fuel efficiency. It regulates engine emissions and also the total vehicle. The new metrics will be based on work done, not just power produced. CO2 emissions will be measured in grams per ton-mile. Fuel economy will also be measured per ton-mile.


Vehicle and engine builders have had typical on-highway and vocational truck configurations benchmarked to account for the varying needs of the marketplace. It would be improper and inaccurate to use one set of ton-mile figures for on-highway and all the variations and sizes of vocational trucks. Even using established National Highway Traffic Safety Administration (NHTSA) weight classes would fail to account for application differences in class 8 (33,000 pounds and greater GVWR/GCWR) trucks alone. Freight trailers and dump trailers differ widely, as do tanks and equipment haulers. Not only are they configured differently with different aerodynamics and other characteristics, but their operating profiles differ greatly.

One gallon of diesel fuel creates 22.38 pounds of CO2 when burned completely. It is accepted that if you can reduce the amount of fuel used for each unit of work accomplished, you will reduce the CO2 emitted to the atmosphere. The goal is to reduce CO2 and diesel consumed by 20% from 2014 through 2017. Additional reductions will be announced for model years 2018 and beyond.

The 10 classes for EPA/NHTSA 2014 regulations differ from standard classes 1 through 8. They account for truck configurations and applications as well as weight. Five of the 10 new classes involve class 8 (by weight) vehicles, varying by cab configurations. Only one of those five should concern us: the EPA Class 8, defined as (weight) class 8 vocational trucks. EPA Class 9 includes (weight) class 6 and 7 vocational trucks, while the new Class 10 includes (weight) classes 2b through 5 vocational trucks.

Vocational, or work trucks are considered “heavy heavy-duty,” “medium heavy-duty” and “light heavy-duty,” respectively. Virtually every diesel-powered vehicle we use, from service vehicles based on pickup trucks to heavy dump trucks and prime movers, is covered.

With EPA 2004, 2007, and 2010 regulations, emissions could be measured at the tailpipe. They were absolute limits. But GHG regulations allow for variations from vocation to vocation. It would be unfair to measure a dump truck that travels half the time unloaded with the same yardstick as a hydraulic boom truck that operates continuously at maximum weight. That’s why truck builders and engine makers average their results.

Unlike EPA emissions regulations, “Not every truck has to be compliant, but every truck has to be certified.” According to the EPA, “It’s up to the OEM to ensure they have enough adoption of those [advanced] technologies across the fleet.” Technologies available to truck users run from low rolling resistance and wide base single tires all the way to natural gas or hybrid power.

Demonstrating value

It will be up to the OEM sales organization to demonstrate the value of the various technologies to you, the buyer. Then the OEM can average the mileage improvements and CO2 reduction over the entire range of trucks sold. Not all trucks sold as certified may meet GHG reductions targets, but they will be averaged with those that do.

Technologies will be grouped according to application, as engine- or vehicle-related. Biofuels, alternative fuels, and fuel management technologies, for example, will be measured in test cells according to use-specific test cycles. Those results will determine an engine’s certification of meeting its CO2 standard.

Using results of coast-down and other forms of testing, EPA has assigned baseline values to trucks and efficiency values for devices to be added—or in some cases, removed—from trucks. For work trucks, these could include weight reduction, fuel-efficient tires, idle timers, and vehicle speed limiters.

It will be up to you, the vehicle operator, to maintain each vehicle in its as-purchased condition. On-board diagnostics (OBD) will help assure against malfunctions in the operation of each vehicle compared to its original condition.

Any malfunction or variance in any of 38 systems being monitored will be recorded in the engine computer. If not timely addressed, it could be considered a violation of federal regulations. Even transient malfunctions, such as temporary stoppage of DEF flow at start-up if the fluid is frozen, will be recorded and stored, even if the malfunction indicator light goes out when the DEF thaws. Generally, when the OBD MIL or the check-engine light stays on, the truck should be taken to the shop.

Most OEMs now offer remote diagnostics tied in with the OBD and engine management systems. They can notify your dealer and, if necessary, schedule service and order parts. Whether the OEMs will allow your shop to be tied into their systems remains to be seen.

GHG-certified vehicles will have a compliance sticker on the door, showing their GHG technologies. The sticker and the listed technologies must remain on the truck throughout its useful life, defined as 10 years for all, and 110,000 miles for light heavy-duty trucks, 185,000 miles for medium heavy-duty trucks, and 435,000 miles for heavy heavy-duty trucks.

Paul Abelson is a former director of the Technology and Maintenance Council (TMC) of the American Trucking Associations, a former board member of Truck Writers of North America, and is active in the Society of Automotive Engineers. E-mail [email protected].