2021 X15 Efficiency Series Engine

X15 Efficiency Series (2021)

Power 400 - 500 hp
298 - 373 kW
Torque 1450 - 1850 lb-ft
1966 - 2508 N•m
Certification EPA 2021

When you need to make it to Fresno by dawn…

The X15 Efficiency Series has been able to meet the 2021 EPA and Greenhouse Gas Phase 2 requirements since 2020 and is officially certified to 2021 standards. With over 12 months of product performance in North America – the 2021 X15 Efficiency Series is following the most success 15 liter product launch to date. Building off 3 key product attributes, fleets, operators, and owners can trust the Cummins X15 to deliver where it matters most – their bottom line.


Heavy-Duty Truck Truck Equipment Manufacturers and Body Builders



The 2020 X15 Efficiency Series incorporated key product improvements to meet the 2021 emissions standards. Cummins measures the performance of product launches through metrics like “percent zero touch” and “touches per thousand” in order to quantify product reliability and uptime. The 2020 product launch was the best performing product launch to date, and with minimal changes for the 2021 launch, we expect he trend to continue.
Cummins offers the longest service intervals in the industry – keeping you on the road and out of the service bay. 

Lower Total Cost of Ownership

The X15 Efficiency Series for 2020 and 2021 has demonstrated a 3.5% fuel economy improvement for select customers when comparing their powertrain configuration to the 2019 product. With EX ratings providing up to an additional 1.5% fuel economy improvement in certain duty cycles, and the available of ADEPTTM electronic powertrain features, the X15 Efficiency Series continues to help you get the most out of every drop of fuel. And with the longest service intervals in the industry – you’ll spend less money on maintaining your equipment and get more out of it.

Ease of Operation

The Cummins X15 Efficiency Series makes every driver better. With access to ADEPT features on every Efficiency Series engine (compatible transmissions required) and the available of EX ratings – the X15 powered powertrain operates better than ever. Features like SmartCoast and SmartTorque 2 can be enabled without requiring a unique calibration, and EX ratings provide the next level of powertrain optimization with access to four unique powertrain electronic features.

Complete Coverage When You Need It Most

The X15 continues to be backed by a 2 year / 250,000 miles warranty with complete engine coverage available up to 5 Years / 500,000 miles when purchasing the new Protection Plan Plus Extended Coverage offering.

To help configure your X15 Efficiency Series powertrain, find and contact your local Cummins expert or use Cummins PowerSpec Web to develop your own vehicle spec.

Advertised Horsepower 400-500 hp
298-373 kW
Peak Torque 1450-1850 lb-ft
1966-2508 Nm
Governed Speed 1700 RPM
Clutch Engagement Torque 1000 lb-ft
1356 Nm
Number of Cylinders 6
System Weight 3152 lb
1430 Kg
Engine (Dry) 2961 lb
1343 Kg
Aftertreatment System 191 lb
87 Kg

Called either “standard” or “straight torque” ratings, the following rating choices provide similar performance in all gears.

Rating Horsepower (Kw) Peak Torque Lb-ft @ 950 RPM (n*m)
X15 450 450 (336) 1650 (2237)
X15 450 450 (336) 1750 (2373)
X15 450 450 (336) 1850 (2508)
X15 500 500 (373) 1650 (2237)
X15 500 500 (373) 1850 (2508)


SmartTorque (ST) ratings provide an additional 200 lb-ft torque in the top 2 gears, keeping drivers in the efficient gears longer.

Rating Horsepower (Kw) Peak Torque Lb-ft @ 950 RPM (n*m)
X15 400ST 400 (298) 1450/1650 (1966/2237)
X15 400ST 400 (298) 1550/1750 (2102/2373)
X15 400ST 400 (298) 1650/1850 (2237/2508)
X15 450ST 450 (336) 1450/1650 (1966/2237)
X15 450ST 450 (336) 1550/1750 (2102/2373)
X15 450ST 450 (336) 1650/1850 (2237/2508)
X15 500ST 500 (373) 1650/1850 (2237/2508)


EX Ratings

New EX ratings provide dynamic powertrain performance with additional driveability and fuel economy benefits. EX ratings require the use of an Endurant HD transmission and GPS look-ahead data. With EX Ratings, 1650 lb-ft (2237 N*m) is the maximum torque available in the first 9 gears. 

Rating Horsepower (Kw) Peak Torque Lb-ft @ 950 RPM (n*m)
X15 400EX 400 (298) 1650 (2237)
X15 400EX 400 (298) 1750 (2373)
X15 400EX 400 (298) 1850 (2508)
X15 450EX 450 (336) 1750 (2373)
X15 450EX 450 (336) 1850 (2508)
X15 500EX 500 (373) 1850 (2508)


Torque and Horsepower Curves:

efficiency series torque curves

efficiency series hp curves

  • VGT Turbocharger – Highly reliable and precise design for rapid acceleration
  • XPI Fuel System – High pressure enables multiple injection events per cycle for industry-leading fuel economy and quieter operation 
  • Single-Module™ Aftertreatment System – A compact and lightweight system that offers increased ash capacity and extended maintenance intervals 
  • Fleetguard Fuel And Lube Filters – Superior holding capacity provides better protection and enables longer service intervals 
  • High-Capacity Electronic Control Module – This allows full integration of data inputs from all subsystems, optimizing performance
  • Cummins Engine Brake – With up to 600 braking horsepower, it’s the most powerful in the industry. Stronger braking capacity reduces wear on service brakes and replacement costs
<5.0 MPG
5.0 – 5.9 MPG
6.0 – 6.9 MPG
>7.0 MPG
OIL DRAIN INTERVAL 25,000 mi 50,000 mi 60,000 mi 75,000 mi
X15 OIL DRAIN WITH VALVOLINE PB 30,000 mi 55,000 mi 65,000 mi 80,000 mi
X15 OIL DRAIN WITH CUMMINS OILGUARDTM extensions available extensions available extensions available Up to 100,000 mi
FUEL FILTER* 25,000 mi 50,000 mi 60,000 mi 75,000 mi

If combined percent idle time plus power takeoff (PTO) time is greater than 40% for Shorthaul, Normal, or Light intervals, use the next lower drain interval. 
*For Premium Blue users, the Fuel Filter interval matches the ODI.


<5.5 MPG
5.5 – 6.5 MPG
>6.5 MPG
DPF Ash Maintenance*** 250,000 - 400,000 m 400,000 - 600,000 mi 600,000 - 800,000 mi
DEF 300,000 mi / 6,750 hours
Valvetrain 500,000 mi / 10,000 hours / 60 months
Drive Belts 500,000 mi / 10,000 hours / 60 months
Crankcase Breather N/A
HC Doser N/A

***Cummins recommends using Cummins genuine DPFs over cleaning of the DPF at the DPF ash maintenance interval. Users can experience extended DPF ash maintenance using the DPF maintenance fault lamp (FC5383).

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