Cummins Heavy-Duty and MidRange Products FAQ

Cummins engines are designed to provide the highest levels of performance, durability and dependability at the lowest total cost of operation.

We want you to be as comfortable and confident with Cummins world-class technology as we are, so we've collected the most frequently asked questions about Cummins Heavy-Duty and MidRange products, the Cummins Aftertreatment System, diesel exhaust fluid, and environmental and regulatory issues.

To view the questions and answers online, please use the FAQ below.

Section 1: Engines and Products

1.  Do Cummins engines meet 2013 EPA regulations?

Yes, all Cummins engines are certified to the 2013 United States Environmental Protection Agency (EPA) and Air Resource Board (ARB) regulations. In addition, Cummins Heavy-duty and MidRange engines meet the 2014 Greenhouse gas (GHG) and fuel efficiency rules that take effect in 2014 a full year ahead of schedule.

2.  What is Cummins on-highway Heavy-Duty diesel engine lineup?

Cummins ISX15 is the most popular big-bore engine in the Class 8 truck market. The 2013 ISX15 continues its legacy of proven performance with continuous improvement resulting in a 2% improvment in fuel economy over the 2012 ISX15. The ISX15 incorporates all of the advances from the last 10 years, including the best-in-class 600-bhp Intebrake™ system, and programmable features such as Load-Based Speed Control (LBSC) and Gear-Down Protection (GDP) that allow customers to customize vehicle performance.

The Cummins ISX12 has proven itself in applications from less-than-truckload (LTL) and daycab trucks to mixers, dump trucks and refuse haulers. With over 800 lb-ft (1085 N•m) of clutch engagement torque, SmartTorque ratings that deliver an additional 200 lb-ft of torque in the top two gears, vocational ratings that provide additional torque in the lower gears and options including front- and rear-mounted power take-off (FEPTO and REPTO), the ISX12 is ideal in operations calling for a compact heavy-duty engine.

Both the ISX15 and the ISX12 feature Cummins exclusive XPI fuel system from Cummins Fuel Systems, the proven VGT™ Turbocharger from Cummins Turbo Technologies, and the Cummins Aftertreatment System with SCR technology from Cummins Emission Solutions.  In 2013 the ISX15 and ISX12 benefit from Cummins focus on continuous improvement through the reduction of parasitic losses, improvements in combustion efficiency, fewer active regenerations and changes to gearing recommendations. Improvements to the efficiency of key components like the water and fuel pumps, piston oil ring and piston cooling nozzles as well the use of lower viscosity oils all reduce parasitic losses, allowing increases in engine efficiency as well as optimized engine calibrations and fewer active regenerations combine to result in improved fuel economy of up to 2%.

Both engines are also equipped with Cummins proven On-Board diagnostics system that has been used in thousands of on-road vehicles since 2007.

3.  How have gearing recommendations changed for Cummins Heavy-Duty engines?

Gearing recommendations have changed for Cummins 2013 heavy-duty engines to provide better fuel economy while maintaining safe, driver-pleasing performance. This process, called downspeeding, allows the engines to achieve peak torque at 100 fewer RPMs than previous models.  Each 100 fewer RPMs used equates to roughly a 1% improvement in fuel economy.

For the ISX15 two fuel economy gearing recommendations have been developed, a Maximum Fuel Economy recommendation intended for trucks spending the majority of their time on the interstate in top gear, and a Fuel Economy recommendation that is ideal for regional haul or 2 lane driving.  

In 2013 Cummins ISX15 Gearing recommendations are:

Maximum Fuel Economy:  
ISX15 400-450hp => 1260-1280  RPM @ 65mph

This recommendation is designed for those whose main concern is fuel economy and that will spend the majority of their time on the interstate operating at least 94% of the time in top gear.

Fuel Economy:
ISX15 400-450hp  =>  1370-1400 RPM @ 65mph

This recommendation is intended for general fleets and regional haul operations that operate on both interstates and two lane highways.

ISX15 485-600hp  =>  1400-1450 RPM @ 65mph

This recommendation allows for more power and performance while still providing solid fuel efficiency. Owner operators looking for a balance of performance and fuel efficiency from higher ratings will use this recommendation.

There are three gearing recommendations for the ISX12:

Fuel Economy:  1370 RPM @ 65mph
Performance:  1550 RPM @ 65mph
Vocational: 1700 RPM @ 65 mph

4.  What is Cummins MidRange diesel engine lineup for 2013?

Cummins MidRange engines feature better fuel economy, better reliability and durability. Both the ISB6.7 and the ISL9 feature the VGT™ Turbocharger, the Cummins Aftertreatment System with SCR technology, and a common ECM to manage both the engine and aftertreatment system.  

The ISB6.7 gets better fuel economy than any engine in its class and in 2013 fuel economy increases by up to 1% over the 2012 model.  The addition of an air-intake throttle helps make the EGR system more efficient, leading to the increase in fuel economy.  Cummins focus on continuous improvement can be seen on the ISB6.7 with a new ECM that controls the DEF dosing valve and improvements to the actuator on the VGT turbo, the EGR crossover tube and the orientation of the EGR valve.

With the highest power density of any engine in its class, the ISL9 also makes an additional 1% gain in fuel economy in 2013.  Including heavy-duty features such as replaceable wet liners, roller followers, by-pass oil filtration and targeted piston cooling, the 2013 ISL9 delivers the dependability and reliability required in tough work environments.  The ISL9 features the Cummins XPI fuel system – the same technology that is used on Cummins ISX15 and ISX12 – that is capable of multiple injection events per cycle at ultra-high injection pressures.  The ISL9 also benefits from improvements to the air intake throttle and the actuator on the VGT turbo as well as increased efficiency and reliability of the EGR cooler and a new ECM that controls the DEF dosing valve.

The ISB6.7 and the ISL9 come equipped with NanoNet fuel filters from Cummins Filtration. NanoNet is a two stage fuel filter that exceeds 99.6% filtration efficiency, offers double the contaminant holding capacity and provides approximately 10 times better protection of the engine fuel system. Both engines are also equipped with Cummins proven On-Board Diagnostics (OBD) system that has been used in thousands of on-road vehicles since 2007.

5.  What base warranty and extended coverage options are available for Cummins engines?

Cummins heavy-duty engines, the ISX15 and ISX12, include a 2 year/250,000 mile base engine warranty that covers parts and labor on all warrantable failures of both the engine and aftertreatment with no deductible.  Extended coverage options are available for up to 7 years or 500,000 miles and cover internal components and major engine systems, including the turbocharger, water pump and fuel injectors, as well as, new for 2013, the air compressor, fuel pump and select engine sensors.

The ISL9  base warranty is 2 years/250,000 miles and includes parts and labor on warrantable failures with no deductible. Extended coverage options are available for up to 7 years or 300,000 miles and include internal components and major engine systems including the turbocharger, water pump and fuel injectors. New in 2013, coverage also includes the air compressor, fuel pump and select engine sensors.

The ISB6.7 is covered by a 2 year/unlimited mileage base warranty that includes parts and labor on all warrantable failures with no deductible.  Extended coverage options are available for up to 7 years or 300,000 miles and include internal components, major engine systems, and the turbocharger, water pump and fuel injectors. In 2013 coverage also includes for the air compressor, fuel pump and select engine sensors.

6.   How are Cummins engines supported?

All Cummins engines are backed by Cummins Care, a trusted information source for questions regarding the latest engine, aftertreatment and related technologies. Customers needing assistance can contact Cummins Care at 1-800-DIESELS™ to receive 24/7/365 assistance from a Cummins Care representative. Representatives are prepared to answer all operational questions on topics such as fuel and oil specifications and maintenance intervals and can assist customers with finding the nearest authorized and available service location. Customers also have access to the largest and most capable parts and service network in North America with over 3,500 locations.

7.   What natural gas engines are offered?

The Cummins Westport ISL G is the industry leading natural gas engine offering for the North American on-highway market. The ISL G utilizes the same base engine and key components as the ISL9, as well as Stoichiometric cooled Exhaust Gas Recirculation (SEGR) combustion, leveraging Cummins proven EGR technology to create a high performance natural gas engine without compromising power and torque. Capable of operating on liquid natural gas (LNG), compressed natural gas (CNG) or biomethane, the ISL G is the natural choice for customers wanting a MidRange natural gas engine.

New in 2013 is the Cummins Westport ISX12 G.  The ISX12 G utilizes the same base engine and key components as the ISX12 in conjunction with the Cummins Westport proven SEGR, spark ignition and simple Three-Way catalyst aftertreatment system. Engine braking and manual transmission options are available. The ISX12 G is suitable for a variety of heavy-duty vehicles including regional haul trucks, vocational and refuse applications. Capable of operating on CNG, LNG or biomethane, the ISX12 G began limited production in April 2013, with full production in August 2013.

In 2012 Cummins announced the development of two additional natural gas engines, the Cummins ISX15 G and the Cummins Westport ISB6.7 G.  Both engines will use proven spark-ignited, Stoichiometric cooled Exhaust Gas Recirculation (SEGR) technology. A simple, three-way catalyst will be the only required exhaust aftertreatment. The ISX15 G and the ISXB6.7 G will run on compressed natural gas, liquefied natural gas or biomethane.

The ISX15 G is expected to be in limited production in 2016, while the ISB6.7 G is expected to begin production in 2015.

8.   What is Cummins approach to meeting EPA standards?

Cummins unique capability allows for a complete package that includes a highly capable base engine coupled with the integration of core technologies for fuel systems, air handling, filtration, electronic controls and exhaust aftertreatment for both particulate matter (PM) and oxides of nitrogen (NOx).  Only Cummins has the key component technologies in-house.

Having the key component technologies in-house allows Cummins to build on our proven engines and subsystems to meet future standards. In fact, it’s what has allowed Cummins to meet 2014 Fuel Efficiency and Greenhouse Gas standards a full year early, in 2013.

9.  What are the benefits of Cummins technologies?

Fuel Economy is a significant advantage of Cummins technology.  Customers will see Cummins 2013 diesel engines deliver up to 2% improvement in fuel economy.

Performance: Cummins Heavy-Duty and MidRange products deliver better power and torque.

 Engine Model    Horsepower Range
 Diesel Engines 
ISX15   400 – 600 Hp
ISX12  310 – 425 Hp
ISL9 260 – 380 Hp
ISB6.7200 – 325 Hp
Natural Gas Engines 
ISX12 G 320 – 400 Hp
ISL G 250 – 320 Hp

Reliability:  When it comes to reliability, experience matters.  For Cummins, experience is derived from millions of miles of product testing that occurs in more than 230 test cells around the world, as well as through millions of miles of real-world engine use.  In fact, Cummins has produced more than 388,000 engines utilizing SCR, more than 965,000 SCR systems, more than 1.2 million diesel particulate filters, and more than 1 million cooled EGR engines that are in use in a wide variety of applications, geographies, and climates around the world.

10.  What is the value of the fuel economy improvement to a Cummins customer?

Heavy Duty Truck Example:

Assuming 6 mpg as the base case, at 120,000 miles per year and diesel fuel at $4.10 per gallon, 2% improvement in fuel economy is worth just over $1600 per truck per year.

 2% Fuel Economy Improvement   
 Fuel Savings $ SavingsCO2 Savings
1 Heavy Duty Truck   400 gallons  $1640   4 tonnes
100 Heavy Duty Trucks 40,000 gallons$164,000400 tonnes

Medium Duty Truck Example:

Assuming 8 mpg as the base case, at 25,000 miles per year and diesel fuel at $4.10 per gallon, a 2% improvement in fuel economy is worth $254 per truck per year

 2% Fuel Economy Improvement   
 Fuel Savings $ SavingsCO2 Savings
1 Medium Duty Truck 62 gallons  $254  0.62 tonnes
100 Medium Duty Trucks    6,200 gallons$25,400  62 tonnes

11.  Are there any changes to maintenance intervals for 2013 engines?

Maintenance intervals for Cummins MidRange ISL9 and ISB6.7 are unchanged in 2013.

For Heavy-Duty engines, the ISX15 and ISX12, the DEF Filter maintenance interval has been extended to 300,000 miles. ISX15 oil drain intervals have increased by 5,000 miles for all duty cycles. This change extends oil drain intervals from 25,000 to 30,000 miles for normal duty cycles, from 35,000 to 40,000 miles for light duty cyles, and from 15,000 to 20,000 miles for severe duty cycles.

For both the ISX15 and the ISX12, the use of Valvoline Premium Blue CJ-4 oil may be used to extend oil drain intervals by an additional 5,000 miles for light and normal duty cycles.

Cummins has updated oil specifications and now allows the use of low viscosity 5W30 or 10W30 oils. These low viscosity oils can improve fuel economy by up to 1% and are also acceptable for heavy-duty engines produced prior to 2013.

As always, for complete maintenance information please consult your Owner’s Manual or Operation and Maintenance Manual. QuickServe Online, Cummins online parts and service information source, is also an excellent source of information.

Section 2: Cummins Aftertreatment System

1.  What makes up the Cummins Aftertreatment System?

There are four major components:

Cummins Aftertreatment System

2.  What is Selective Catalytic Reduction (SCR)?

SCR is a technology for converting the oxides of nitrogen (NOx) emissions from a diesel engine into nitrogen gas and water. Cummins Aftertreatment System uses diesel exhaust fluid as a chemical reductant, which converts to ammonia in the exhaust stream and reacts with NOx over a catalyst.

3.  What is Diesel Exhaust Fluid (DEF)?

DEF is a mixture of 32.5% urea in a solution of dionized water.

4.  How much DEF will be required?

DEF consumption is 3 – 4% of fuel consumption dependent on vehicle operation, geography, and climate.  

5.  What size DEF tank is required on a vehicle?

The DEF tank size and location is determined by the vehicle manufacturer/OEM.  However, Cummins has provided installation guidelines to the OEMs and recommended that the DEF tank size be at least 6% of the fuel tank volume (i.e. if the fuel tank is a 300 gallon tank, the DEF tank should be at least 18 gallons).

In general, the DEF tank size for a medium duty application is typically 5 – 15 gallons.  For a heavy-duty application the tank size is generally 15 – 25 gallons.

6.  What happens if the vehicle runs out of DEF?

Aftertreatment Systems that use DEF have two indicators on the dash that alert the driver to the quantity of DEF on board.  First, there is a DEF gauge very similar to a fuel gauge that indicates the level of DEF (i.e. full, half, quarter, etc.).  Second, there is a DEF Lamp that illuminates and/or flashes when the contents of the DEF tank reach specific thresholds.

The DEF Lamp will illuminate when the tank reaches 10% capacity. In order to correct this, the DEF tank must be filled to at least 20%.

The DEF lamp will flash when the level drops below 5%. This alerts the driver that additional DEF is needed. In order to correct this, the DEF tank must be filled to at least 15%.  Cummins recommends filling the tank to full capacity.

When the DEF tank reaches 2.5% of capacity the DEF Lamp will continue to flash and the Check Engine Lamp (Amber Warning Lamp) will be illuminated. There will be a 25% reduction in engine torque performance. In order to correct this the DEF tank must be filled to 12.5% of its capacity; Cummins recommends filling the DEF tank to full capacity.

If the DEF level drops to 0% and the truck is in motion the DEF Lamp wil continue to flash and the Check Engine Lamp (Amber Warning Lamp) will remain illuminated. The MIL lamp may also illuminate at this point. Available torque will be limited to 60% of peak torque. This additional 15% torque derate will be ramped in at 1% per minute. In order to correct this the DEF tank must be filled to at least 10% of its capacity.

When the DEF tank is at 0%, if the vehicle is intentionally shut down, or the vehicle has idled for 1 hour, or the vehicle has been refueled, the DEF Lamp will continue to flash, the Check Engine lamp will remain illuminated, and the Stop Engine Lamp will illuminate. Available torque will remain limited to 60% of peak torque and the vehicle speed will be limited to 5 mph.  In order to correct this, the DEF tank must be filled to at least 10%.  Cummins recommends filling the DEF tank to full capacity. Carrying a few gallons of DEF will enable operators to meet the DEF tank capacity requirements necessary to get to a refill location.

7.  Does DEF freeze?

Yes.  DEF begins to freeze at 12° F (-11° C). The Cummins Aftertreatment with SCR is designed to provide heating for the DEF tank and supply lines which reduce the melting time for frozen DEF.

8.  How do I keep DEF from freezing? What happens if DEF freezes in the tank on the vehicle?

During vehicle operation, the SCR system is designed to provide heating for the DEF tank and supply lines.

If DEF freezes when the vehicle is not in operation, start up and normal operation of the vehicle is not inhibited. Heated lines in the SCR system are designed to quickly return the DEF to liquid form and the operation of the vehicle is not impacted.

9.  Does DEF smell?

DEF may have a slightly pungent odor similar to that of ammonia.

4.  Should I be concerned about handling DEF?

No.  DEF is a non-toxic, non-polluting, and non-flammable substance.  DEF is safe to handle and store and poses no serious risk to humans, animals, equipment or the environment when handled properly.

5.  Is DEF available for customers to purchase?

Yes, DEF is available for customers to purchase.  Since 2003, Cummins Filtration has offered DEF in bulk, 330-gallon plastic totes, 275-gallon disposable totes and 55-gallon plastic drums.  In June 2009, the Fleetguard DEF product line was expanded to include smaller package sizes, including 1 and 2.5 gallon bottles.  

In early 2010 Cummins Filtration and Ashland Consumer Markets (Valvoline) announced an alliance to package, market and distribute DEF, further expanding the availability of DEF in North America.  Since April 2010 Fleetguard®-Valvoline® Air Shield™ DEF has been offered through the Cummins and Valvoline distribution channels in the United States and Canada.

Outside of Cummins, DEF is available through a wide variety of sources.  DEF can be purchased online, at-the-pump at major truck stops, and in small volume containers at more than a thousand retailers throughout North America.

6.  What is the expected price for DEF?

Pricing for DEF is highly dependent on packaging size, with bulk pricing being lower than smaller package sizes.  Currently, the at-the-pump price for DEF is $2.79/gallon with bulk pricing below $2.00/gallon in certain locations.  

For more information on pricing or to obtain a quote for DEF, contact Cummins Filtration at 800-22-FILTERS or visit

Section 3: Environmental & Regulatory

1.  What are the On-Board Diagnostics (OBD) standards that take effect in 2013?

The 2013 EPA regulations call for the addition of On-Board Diagnostics (OBD) to all on-highway diesel engines. OBD is designed to monitor the performance of the vehicle’s emission system to help detect issues, recognize faults and ensure optimal performance. If the system detects any emissions-related malfunctions, it will alert the operator through a dash lamp known as the Malfunction Indicator Lamp (MIL).

MIL lamp The MIL illuminates when the On-Board Diagnostics system detects a malfunction related to the emissions control system. An illuminated MIL indicates that the engine and aftertreatment system should be diagnosed and serviced at the next available opportunity. 
 MIL lamp and stop engine lamp

If the MIL is illuminated with the red Stop Engine Lamp, the vehicle should be stopped as soon as it is safe to do so and taken to an authorized Cummins location for repair.

2.  What are the benefits of OBD to the operator and/or fleet owner?

Enhanced diagnostic systems are required to help keep sophisticated engine and aftertreatment control systems operating at their peak. These diagnostics result in an improved capability to detect potential problems early, which allows owners to schedule their downtime before problems result in noticeable symptoms. For example:

  • OBD requires the addition of a thermostat monitor. This monitor can detect leaky thermostat and drive a repair during the summer, before anything could be noticed by the operator in the fall or winter.
  • Early detection and repair of failures that may impact fuel economy can prevent and minimize the impact to a fleet’s operating costs.
  • Finally, improved fault isolation can lead to faster repair times.

3.  What are the 2014 Fuel Economy and Greenhouse Gas Regulations?

Greenhouse Gas Emissions Regulations were finalized in August 2011.

Cummins announced in August 2011 that our products will meet the 2014 standards a year early allowing us to meet both OBD and GHG regulations in 2013. Cummins has received 2013 certification for its entire on-highway engine lineup.
Meeting the standards early allows Cummins to deliver additional fuel economy benefits to end-user customers and to provide installation stability to OEM customers.
Rule documents both vehicle and engine standards and divides covered vehicles (all vehicles at 8,500 lbs gross vehicle weight) into 3 categories:
  • Medium and heavy-duty pick-ups and vans
  • Vocation vehicles like fire and emergency vehicles
  • Truck tractors that pull trailers
Reduction levels and timing for each category are:
  • Combination tractor/trailers – standards begin in the 2014 model year and achieve up to 20% reduction in carbon dioxide (CO2) emissions and fuel consumption by 2017. This reduction includes separate tractor engine standards – which for heavy-duty engines are a 3% improvement by 2014 followed by a total of 6% by 2017
  • Heavy-duty pickup trucks and vans – standards phase in starting in the 2014 model year and achieve up to a 15% reduction by 2018 model year
  • Vocational vehicles – such as mixers, dump trucks and refuse haulers need to achieve a 10% reduction in fuel consumption by 2017. This reduction includes separate vocational engine standards – which for medium heavy-duty engines are a 5% improvement by 2014 followed by a total of 9% by 2017

5.  What are the greenhouse gases regulated under this rule?

CO2 is the primary gas regulated.  Engines also have methane (CH4) and nitrous oxide (N20) emissions (which are also GHGs) caps.

6.  What will change on Cummins engines for 2014?

For 2014, don’t expect anything more than the continuous improvement you see Cummins making today to our products. ECM calibration improvements as well as the current technologies of high pressure common rail fuel systems like XPI and HPCR, the VGT Turbocharger, and cooled EGR and SCR are what you will continue to see in 2014.

7.  Where are Cummins 2013 engines available?

Cummins 2013 Engines are available with the following customers:

 ADL  Navistar RV
 American La France NABI Bus
 Badger Equipment New Flyer Bus
 Capacity of Texas Nova Bus
 Cargotec (Ottawa/Kalmar) Newell Coach Corp
 Chrysler Oshkosh Truck
 Crane Carrier Pierce
 El Dorado National RPM Tech
 Elgin Rosebauer
 E-One Schwarze
 Ferrara Seagrave
 Global Sweepers Sunny D.
 Foretravel Spartan Chassis
 Foton America Bus Co. Sutphen Corp
 Gillig Bus Taylor Rigs 
 Grove Temsa
 HME Terex
 Kimble Chassis TICO
 Kovatch (KME) Tiffin
 Link-Belt Vanhool
 Lodal Wausau Equipment