2010 Emission Systems

Truck OEMS have taken two different approaches to controlling diesel emissions

Vehicles in 2010 that will use DEF will have two indicators on the instrument cluster that will alert the driver to the quantity of DEF on board, say Cummins officials. One will be a new DEF gauge, very similar to a fuel gauge today, which will indicate the level of DEF (i.e. full, half, quarter, etc.). The second indicator will be a new DEF low-level warning lamp that will illuminate when less than 10 percent of DEF is in the tank, advising driver that a DEF top off will be required.

When and if the tank is run dry, the engine will be power and speed limited until the DEF is replenished, say Detroit Diesel officials. Once the tank has been refilled, the engine will resume normal power levels.

Under no circumstances will the engine shut down or be prevented from restarting as a result of running out of DEF, stress all engine builders.

"At no time will we strand a driver with no DEF, as opposed to a no-fuel scenario - when you are going exactly nowhere," says McKenna.

The distribution infrastructure for DEF is in place. DEF is widely available at many locations, including truck stops, truck and automobile dealerships, engine distributors, diesel service stations, fueling stations, fuel distributors, auto parts stores and other retail locations. Pilot Travel Centers opened the first DEF dispensing at pumps at fuel plazas in several locations.

Engine manufacturers stress that DEF should not be "home brewed," as this can cause serious problems. DEF has strict requirements for maintaining concentration and purity of ingredients that is critical to the proper functioning and longevity of the SCR system. Furthermore, the OEMs require that DEF used with their SCR systems meet all ISO (International Organization for Standardization) specifications, as well as API (American Petroleum Institute) quality certification requirements.


DEF is affected by cold weather, and as such, the DEF system requires a heating element, says DTNA's Thomas. During vehicle operation, SCR systems are designed to provide heating for the DEF tank and supply lines.

Paccar, by way of example, utilizes heat generated from the engine to ensure the solution remains at operational consistency at the coldest temperature extremes.

Because DEF is 67.5% deionized water, it will freeze into a crystalline-type (slushy) material, and begins freezing solid at extended periods below 12 degrees Fahrenheit," explains Mack's McKenna. If DEF freezes, the engine will start and run properly. The freezing and unthawing of DEF will not cause degradation of the product.

"Let's suppose we parked a truck overnight or over the weekend in the Upper Peninsula of Michigan in the middle of January where it is unarguably cold," he says. "Safe and good practice would have the truck either plugged in (block heater) or running a timed APU, so the engine coolant is already going to be about 60 degrees Fahrenheit. Upon engine start, coolant from the engine will be circulated through the DEF tank to thaw or re-liquefy product."

In addition to EPA allowances for cold weather starts, McKenna notes that cold engines produce an infinitesimal amount of NOx.

DEF stored at extremely high temperatures for extended periods of time will slowly degrade. Shelf-life for DEF is up to 18 months or greater under normal conditions. Storing in temperature-controlled conditions will add to its shelf life.

DEF, which weighs approximately 9 pounds per gallon, expands by approximately 7 percent when frozen. DEF packaging and tanks are designed to allow for expansion.

DEF is safe to handle and store, and poses no serious risk to humans, animals, equipment or the environment when handled properly, say DEF producers and suppliers. If spilled, the DEF should be contained and absorbed with an inert, non-combustible absorbent material such as sand. The material should be shoveled in to a suitable container for disposal.

Spills into a drain should be avoided. If DEF is spilled into a drain, the drain should be thoroughly flushed with water. If DEF is spilled on a vehicle, the area should be rinsed with water.


Manufacturers of SCR and EGR emissions technology each tout the advantages their systems provide. Among them: performance, durability and reliability, plus a reduced carbon footprint. SCR technologies have been proven to lower operating costs through improved fuel economy in most applications. Neither system impacts engine warranty.

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