The 6.7L Cummins arrived around 2007.5, and one of the most important dividing lines within its run is the addition of a DEF-based selective catalytic reduction system. Roughly speaking, the early 2007.5 to 2012 trucks use a diesel particulate filter without DEF, while the 2013 and newer trucks added the DEF system. Understanding this split helps buyers know what to expect from ownership, from routine refills to how the emissions hardware behaves and how the truck drives day to day. It also explains why two 6.7L Cummins trucks only a few years apart can have noticeably different maintenance routines. Here is how the two eras differ and what stays the same across both.
The early trucks (roughly 2007.5 to 2012)
The first 6.7L Cummins trucks introduced the larger inline-six with a diesel particulate filter but did not yet use a DEF-based SCR system. To meet emissions without DEF, these trucks lean more heavily on EGR and in-cylinder strategies, which can place more soot load on the DPF and, in some driving patterns, mean more frequent regenerations. Owners of these trucks manage regeneration cycles and keep an eye on the emissions hardware, but they do not deal with DEF refills. For buyers who prefer to skip DEF entirely, these are the years to consider.
The later trucks (roughly 2013 and newer)
Around 2013, the 6.7L Cummins adopted selective catalytic reduction using diesel exhaust fluid, or DEF. SCR converts nitrogen oxides into harmless nitrogen and water, which allows the engine to run more efficiently while meeting stricter standards, and many owners find the SCR trucks run cleaner and can be easier on the DPF. The trade-off is that owners now manage DEF refills as routine maintenance, and the SCR system adds sensors and components, such as NOx sensors and DEF injectors, that must stay healthy for the truck to run without derating.
What stays the same across both
Both eras share the fundamentals that make the Cummins a Cummins. The inline-six layout, the stout bottom end, and the intake grid heater for cold starts, not glow plugs, carry through unchanged. The early 6.7L Cummins used the well-regarded Bosch CP3 high-pressure pump, which is a durability asset across this range before the later switch to the CP4.2 around 2019. Regardless of year, keeping the emissions system healthy, the cooling system in good shape, and the fuel clean is central to trouble-free ownership.
Living with the emissions hardware
On either era, regular highway driving helps regenerations complete and keeps the DPF healthier. Addressing emissions faults promptly, rather than ignoring warning lights, prevents the speed derates that a neglected system can trigger. On the DEF trucks, use quality DEF and keep the tank topped off, since running out will limit the truck. On the pre-DEF trucks, pay attention to how often the truck regenerates, as very frequent regens can indicate a developing issue. Neither system is difficult to live with when maintained as designed.
Which era suits you
The early trucks appeal to buyers who prefer not to manage DEF and who want a slightly simpler emissions setup, though they still have a DPF to maintain. The later trucks add DEF but often run more efficiently thanks to SCR. On any 6.7L Cummins, confirm the emissions system is functioning and regenerating normally, review maintenance history, and check the cooling and fuel systems. Both eras are strong, capable trucks with the classic Cummins torque character when properly cared for.
Frequently asked questions
When did the 6.7L Cummins start using DEF?
The 6.7L Cummins added a DEF-based SCR system around 2013. Earlier trucks from roughly 2007.5 to 2012 use a diesel particulate filter but do not use DEF, relying more on EGR to meet emissions.
Is a pre-DEF 6.7L Cummins better?
Neither era is simply better. Pre-DEF trucks avoid DEF refills but lean harder on EGR and the DPF, while SCR trucks add DEF but often run more efficiently. Condition and maintenance matter most on either.
Does the 6.7L Cummins use glow plugs?
No. Like all Cummins diesels, the 6.7L uses an intake grid heater to warm incoming air for cold starts rather than glow plugs.
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