The top concern of fleets using low-emission engines equipped with exhaust gas recirculation (EGR) systems is the 3 to 5% loss in fuel economy caused by this technology. However, both truck and engine OEMs are using a variety of tactics to try and minimize such fuel losses. Detroit Diesel Corp. (DDC), for example, equipped its Series 60 EGR engine with a new low-profile gear train and other lighter-weight parts to offset the higher weight of EGR components. End result: DDC's 2,585-lb. Series 60 EGR engine actually weighs 65 pounds less than the pre-EGR design. The company said it continues to improve the EGR combustion process and fine-tune the engine's software to minimize fuel economy losses. For example, a truckload customer operating one of DDC's EGR engines geared to run at 72 mph last winter averaged 6.91 mpg compared to the average 7 mpg its pre-'02 engines achieved. Cummins said it is using Load-Based Speed Control (LBSC) engine software to improve fuel economy. LBSC limits usable engine speed during low and intermediate power requirements, but allows the engine to operate up to 2,000 rpm and make downshifts at higher rpms when climbing hills. Those control settings allow the EGR engine to operate at maximum fuel economy, Cummins said, to the point where some fleets using LBSC report a fuel economy loss of zero to just 0.5%, instead of the expected 3 to 5%. International Truck & Engine Corp. redesigned its 9000i Series Class 8 tractor over the last two years to help offset fuel penalties associated with EGR. It improved the 9000i's aerodynamics by 14%, which, in turn, improved fuel economy 5%. International truck group president Steve Keate told Fleet Owner better integration between drivetrain and engine can cut fuel use as well, and that such spec'ing strategies will become even more critical in 2007.