When coupled with an Endurant automated manual transmission, the X12 gets the new EX ratings package, providing an additional 1.5% fuel efficiency. - Photo: Cummins

When coupled with an Endurant automated manual transmission, the X12 gets the new EX ratings package, providing an additional 1.5% fuel efficiency.

Photo: Cummins


Cummins has revealed its EPA 2021 emissions-compliant on-highway engines. The latest versions of the X12 and X15 powerplants combine new fuel- and cost-saving features with the proven architecture of the X-series platform. Cummins says customers will see better fuel efficiency across the entire engine lineup along with more uptime and greater reliability. Cummins announced the 2021 lineup at a virtual press event Oct. 13.

Both the X12 and the X15 engines will deliver better fuel mileage for 2021, with the X15 Efficiency up as much as 3.5% over the 2019 version. Customers opting for the X15 Performance series can still get up to 2% improved fuel economy compared to the EPA 2017 version, Cummins says.

X12 buyers will see a 2.5% potential gain in the base configuration through hardware changes with a possible 1.5% further improvement when spec’d with newly available EX ratings for 2021, according to Cummins.

“For a customer getting 6 mpg on a truck that drives 100,000 miles a year, a 2% improvement will save approximately 326 gallons of fuel at $3 a gallon. That’s almost $1,000 savings per truck, not to mention a reduction of over 7,300 pounds of CO2,” said Nick Roth, Cummins’ director of national accounts. “The X12 is also a more efficient product. Compared to the ISX 12, customers with the 2021 X12 can see as much as an 8.5% better fuel economy.”

EX Ratings Expand Fuel Savings

Cummins has added several features that take advantage of the integration between the engine and the Endurant transmission. The EX ratings package build on standard integrated powertrain features like SmartTorque2 and SmartCoast with several new features: On Ramp Boost, Predictive Engine Braking, Predictive Gear Shift and Dynamic Power.

  • On Ramp Boost uses GPS to sense when the truck is entering an on ramp then temporarily opens up maximum torque for faster merging speeds. It automatically returns the vehicle to its normal settings once the vehicle reaches highway speed.
  • Predictive Engine Braking looks at the grade ahead and can engage engine brakes early to aid in maintaining a desired road speed.
  • Predictive Gear Shift scans GPS data to seamlessly match the best gear for the terrain ahead ensuring there’s enough speed to climb oncoming hills. This keeps the truck closer to its cruise speed longer resulting in shorter trip times.
  • Dynamic Power adjusts engine torque so lighter trucks operate like heavier vehicles on grades. This provides fuel savings on lightly loaded vehicles by delivering consistent performance for operations with varying or diminishing loads.

“The previous adaptive features that required a unique engine calibration will be automatically enabled for the X12 EX ratings, so fleets will have access to additional efficiency-focused features like SmartCoast and SmartTorque2 by default,” said RaNae Isaak, Cummins’ powertrain and total cost of ownership consultancy leader. “Customers will still have access to these features in non-EX ratings. They simply can enable them after delivery.”

The 2021 X15 Performance Series will offer select powertrain features that were previously unavailable above 500 horsepower. Features such as SmartCoast, Predictive Cruise Control and Predictive Road Speed Governor will be available for customers with automated manual powertrains in 2021.

The X15 efficiency series will be available from 400 to 500 hp, with a mix of standard SmartTorque and EX ratings. The Performance Series offers ratings from 525 to 605 hp, providing a simple split between the two engines, said Isaak. “We focused on making it easier for dealers to help customers spec the right equipment, for fleets to differentiate between powertrains, and for operators to drive the vehicles more efficiently.”


Previous adaptive features that required a unique engine calibration will be automatically enabled for the X12 EX ratings. Fleets will have access to additional features such as SmartCoast and SmartTorque2 by default. - Photo: Cummins

Previous adaptive features that required a unique engine calibration will be automatically enabled for the X12 EX ratings. Fleets will have access to additional features such as SmartCoast and SmartTorque2 by default.

Photo: Cummins


100,000-mile Oil Change Interval

Both the X15 Efficiency and the X12 already share a 75,000-mile oil-drain interval for trucks getting 7 mpg or better. For 2021, Cummins has increased the oil change interval by 10,000 miles for X15 Performance customers getting between 5 and 7 mpg.

Customers who participate in the Cummins OilGuard oil analysis program can extend their oil change intervals up to 100,000 miles with regular sampling if the oil maintains all its characteristics.

“We have a lot of data from the field for many different duty cycles that show we can safely extend the intervals,” said Kris Ptasznik, Cummins’ heavy-duty on-highway product manager. “OilGuard has done that and the more data we get in, the more comfortable we are with extending intervals.”

Ptasznik said no special engine oil is required provided it meets Cummins’ standards. “We have had customers test with a multitude of oil suppliers other than the Valvoline Premium Blue,” he said. “As long as the samples come back good, then we will let them extend to where ever they need to go.” 

For all 2021 engines, Cummins has aligned the service schedules for both the fuel filter and oil changes so customers won’t have to plan separate maintenance intervals.

Hardware Changes


Cummins' EPA 2021 X15 Performance Series now goes 10,000 miles further on an oil change and gets 2% better fuel economy.  - Photo: Cummins

Cummins’ EPA 2021 X15 Performance Series now goes 10,000 miles further on an oil change and gets 2% better fuel economy. 

Photo: Cummins


Cummins fans won’t notice much difference in the outward appearance of the engines. Much of what has changed or been upgraded is internal, electronic, or in the air handling systems. Some material modifications were made to the X12, such as a different alloy for the crankshaft, along with improved engine breathing, increased compression ratio, and modified ring packs to improve overall efficiency, Ptasznik noted.

“The EX ratings available to customers with the 2021 X12 come via a new electronic control module,” he said. “Also newly available with the X12 is the Cummins connectivity module called Acumen. It offers customers another path to the Cummins suite of connectivity features and can provide the lookahead data needed for the EX ratings.”

Cummins has updated some of the X15 Performance Series’ air handling characteristics for the engine, including leveraging EGR flow for engine brake assistance. The air handling system is updated for better compression ignition and engine efficiency and parasitic and frictional losses are reduced by improving the power cylinder, reducing the water pump speed and resizing some critical components, Cummins says.

It also gets a larger thrust bearing for improved durability. And like the X12, the X15 comes with the new ECM and the available Acumen module.

“And for driver comfort, we have reduced engine noise at idle and also made enhancements to engine shut down,” said Ptasznik. 

“Cummins’ 2021 heavy-duty products were designed with three core deliverables in mind: increased uptime, better overall total cost of ownership, and improved drivability,” says Brett Merritt, vice president of Cummins’ on-highway engine business. “By delivering on these focus areas, Cummins’ products will offer better performance for the customer’s bottom line.”





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