Engine Spotlight

By John Baxter | January 03, 2011

He says fuel mileage normally improves as much as 5 to 6 percent over ’07 engines and Cummins has been able to reduce DEF consumption to just more than 2 percent of fuel consumption. Because of lower stresses on the oil, he adds, “We expect we’ll be able to stretch oil drains.”

Ellison recommended the ISX 500ST as the ideal engine for owner operators. With 500 peak horsepower, it gives 1650 lb.-ft. of torque until reaching the top two gears, when Smart Torque technology increases available torque to 1,850 lb.-ft.

Spec’ing the ISX for efficiency

Zack Ellison of Cummins describes the 600-hp ISX 15-liter engine (pictured), producing 2,050 lb.-ft. of torque, as the ultimate owner-operator engine. Of course, many owner-operators spec a more practical power level, like 500 or 550 hp, with Cummins’ SmartTorque option. This gives 1,650 lb.-ft. up to the top two gears, where 1,850 lb.-ft. becomes available.

Josh Davis, vice president of operations for Davis Express, a mid-size reefer operation, says his fleet has a 2010 Kenworth T700 equipped with a 450-hp ISX with a SmartTorque rating of 1,550/1,750 and an Eaton Ultrashift transmission. After break-in, fuel mileage is just under 6.9 mpg, he reports. Earlier vehicles with 2007 engines are getting about 6.5 to 6.6 mpg. With the 2010, DEF consumption has been 2 to 2.5 percent of fuel use, dropping when Cummins recalibrated the engine.

The truck’s only problem has been a check-engine light brought on by a failed sensor that was quickly replaced at the dealer. “The truck has been very reliable and the driver likes it,” Davis says. “It has good throttle response and performs well on the hills.”


Advertised horsepower: 400-600 hp

Peak torque: 1450-2050 lb.-ft.

Governed speed: 2200 rpm

Clutch engagement torque: 1000 lb.-ft.

Number of cylinders: 6

Bore and stroke: 5.4 x 6.7 in.

Oil system capacity: 14 gallons

Standard oil change interval: 25,000 miles

Engine dry weight: 2,964 lb. (1,344 kg)

Aftertreatment system: 222 lb. (101 kg)

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