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    Exhaust gas recirculation (EGR) lowers the engine's combustion temperature, thus lowering nitrogen oxide (NOx) levels.

At its press conference during the World of Concrete, executives from Navistar announced their decision to use EGR in International Trucks with proprietary MaxxForce engines. International will use only Advanced EGR to meet 2010 EPA diesel exhaust emission standards. That means Cummins engines, which will use SCR in addition to EGR, will not be offered in their 2010 trucks.

Jim Hebe, senior vice president of Navistar, aggressively defended Advanced EGR, despite all competitors' decisions to use SCR. The added SCR equipment adds weight and complexity and makes the operator, not the manufacturer, responsible for achieving compliance, said Hebe. Urea forms slush at 13º F, requiring thermostat-controlled heaters as part of the SCR equipment. (If the DEF becomes frozen, EPA allows idling until enough fluid is liquefied by the heater.)

Competitors counter they will use the same proven engine architecture as the 2007 engines, but with improved fuel economy. SCR requires less cooling than EGR, saving as much as 300 pounds. Fuel economy with SCR is claimed to be as much as a 4% to 5% improvement.

Preliminary estimates from Volvo, parent of Mack Trucks, indicate prices for 2010 trucks with SCR will range from $6000 to $10,000 higher than current models.

Another factor in the selection process is DEF availability. Over-the-road operators have concerns about DEF availability and drivers keeping DEF tanks full. But these concerns may not be as valid for domiciled fleets, such as concrete producers'.

The marketplace will ultimately determine the success or failure of either strategy, as the economy recovers and truck purchasers make their decisions. But now is the time you should ask questions.

Paul Abelson is a former director of the Technology and Maintenance Council of the American Trucking Association and is currently on the Board of Truck Writers of North America. To contact him,