Detroit Gen 6 Engines: What EPA 2027 Really Means for Fleets
The episode explains how Detroit’s Gen 6 heavy duty engines meet EPA 2027 emissions rules through evolutionary improvements, while maintaining reliability, improving efficiency, and minimizing disruption for fleets.
Episode 369: This conversation with Daimler Truck’s Mike Young explores the Detroit Gen 6 engine platform and how it prepares fleets for the EPA 2027 emissions standards by building on nearly 20 years of proven aftertreatment technology.
Young explains that the Gen 6 engines focus on reducing NOx through improved thermal management, a new pre‑SCR system, as well as incremental enhancements carried over from Gen 5. These changes aim to maintain or slightly improve fuel economy depending on idling habits, reduce maintenance surprises, and ensure technicians and parts suppliers experience minimal disruption.
With millions of test miles already accumulated and careful planning for dealer and service‑network readiness, the Gen 6 platform is positioned as a reliable, efficient evolution rather than a disruptive overhaul.
Links
- Detroit Gen 6 Engine Gen 6 Engine | Demand Detroit
- Daimler Truck North America Start | Daimler Truck North America
- Daimler Truck (global) Home | Daimler Truck
- Watch the Video Version
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Transcript of Episode
Jamie Irvine
Welcome to The Heavy Duty Parts Report. I’m your host, Jamie Irvine. In this episode, we’re going to dig into one of the most important powertrain developments in the heavy-duty industry in quite a few years. We’re going to talk about the Detroit Gen. 6 engine platform, what it means for fleets technicians, the parts people that one day will have to supply parts for it as this EPA 2027 deadline approaches. So to help me with that, my guest today is Mike Young. He’s the Powertrain and Safety Product Marketing Manager at Daimler Truck. Mike, welcome to The Heavy Duty Parts Report. So glad to have you here.
Mike Young
Yeah, thanks for having me. I’m excited to get to talk more about these new engines coming up.
Jamie Irvine
Yeah, it’s a big development. For listeners who may not be like deep into engine development can you give us just the high level overview of what this Gen. 6 engine really means and what are some of the changes that we’re going to see?
Mike Young
Sure. So the Detroit Gen. 6 is really the sixth evolution or sixth generation of our heavy-duty H-DEP lineup. So we launched these engines back in 2007 and since then we’ve made updates in 2010, 2013, 2017, 2021, most of those were focused around updating fuel economy improvements, general improvements to improve overall reliability, meeting emissions milestones as they came up. Gen. 6 is the one that’s addressing NOx emissions for the first time in really almost 20 years. And NOx emissions back in 2007, 2010, that’s whenever DPF systems, SCR systems were brought online. And now, about 17 years later, is the first time we’re making changes to those kinds of systems again. So it brought a large development update across, you know, our engines and aftermath systems to make sure that they’re adapted to meet the more stringent emissions coming up. And these were also evolutionary designs. So it wasn’t a whole new setup or, you know, extremely new technology that were a lot of the technology we’re bringing on for 2027 was incremental improvements over things we’ve been doing for years that have allowed us to get down to lower emissions and get down to improving overall efficiencies, steps at a time as it gets more and more difficult over the years to make large improvements. So we’re finding things that work and we’re bringing them forward. We’re expanding them into different applications. And a lot of what we’ve done over the previous generations enabled us to have the simpler solutions we have coming up for 2027.
Jamie Irvine
Okay, so let me understand something. The regulatory requirements that are being put into place, they gave you the target, but they didn’t dictate how you get there. Is that correct?
Mike Young
Yeah, that’s a fair way to put it.
Jamie Irvine
Okay, so I think that when I talk to people about this, there is a little bit of anxiety about it because anybody who lived through the previous one 20 years ago knows how how disruptive, how much change it was, how much added cost there was in maintaining these after treatment systems. What I’m hearing you say is that this time around, a lot of the technology was already developed and in place. Talk me through this incremental improvement and how that might impact or why maybe that is a reason for us to not have as much anxiety about this change.
Mike Young
Sure. So one of our favorite things to do when we talk about our new aftertreatment system is coming up is we call it known technology. We have the same base aftertreatment system we have today. So from what we’re calling our pre-SCR down, it’s the same system that we’ve been running for years, above that is going to be a new SCR system. And the reason why we’re able to use a technology that isn’t so disruptive of what those systems were in the past, for Detroit, we’re going to package it right on top of the system we already have today, and it’s going to package up underneath the cab. We’re able to really minimize any impacts that people have from body configurations. Most trucks, likely if the side fairings and things like that are in place, they’re not even going to see it or see a difference and continue on with the evolutionary changes. Using technology that we’ve already been utilizing since really the start of the SCR systems were brought out, we’ve gotten almost 20 years of real-world experience. We had them running for years and testing even longer than that. So we’ve gotten a whole lot of experience in understanding how these systems work and have been making incremental changes to them over time just to have been on our aftermath system that we have right now has been out in the market. It’ll be seven years that we’ve had that same system out there. And we’ve been able to improve them over the years to take away some of those initial issues that were popping up with them. Additionally, just the learnings over the years, some of the initial issues that came up weren’t always aftertreatment related as much as it was how specs were configured or how people would operate the trucks. So it’s a whole lot of really good learnings that’s gone into making sure we’re teaching people what the right RPM band is gonna be coming up with solutions to let them idle them less and have them keep operators and drivers comfortable in the cab for different idling solutions that we offer now that weren’t always available in the past. Because one of the things that was detrimental to aftertreatment systems as they came out was running a truck the same way that people always had. And idling a truck for a long time, that’s really one of the worst cases for an aftermath system is you’re not producing the heat and temperature that needs to be going down to that system to burn off hydrocarbon buildups and lead into issues like that. So over the years, we’ve had a lot of learning that’s gone into setting us up for what we’re doing for 2027, which is using a system that’s going to use heat right from the engine to reduce the amount of NOx emissions that we’re sending out into the environment. So it’s really, a lot of evolutionary changes has gone into it to make sure that it’s not as drastic of a change as what people would have had 17 years ago.
Jamie Irvine
Because the Gen. 6 engine is like an evolution of the previous generations, and as you said, you’ve had the opportunity to look behind and say, okay, what did we learn in the past, what specific aspects of the Gen. 5 engine carries over into this new engine? It sounds to me like it’s really only a change to the aftertreatment system, but maybe you could talk us through that.
Mike Young
Sure. So whenever we launched the Gen. 5 engines, it was back in 2021, some of my favorite things that we got to talk about was just the huge step forward that we took in thermal management. And that’s what set us up for making our solutions for 2027 a little bit simpler. So some of the things that went into that were really taking control of how the aftertreatment system function and taking control of how heat went down to them. So a number of improvements that we made years ago that’s helped us have the solutions we have coming out for ’27. One of my favorite was thermos-coasting. And if you think about an aft treatment system doing a regeneration while you’re driving down the road, many times the operator may just notice the light on the dash that the system’s heating up, and they don’t need to do anything with it. One of the areas that we and our great engineering teams discovered was that while driving down the road, if you just come off the throttle going down a hill, that is already cooling the aftertreatment system down substantially and prolonging the amount of time it takes to complete an active regen while driving. And we made some changes to allow us to engage engine brakes without actually slowing the truck down. So sending heat and temperature down to the aftermath system to complete those regens faster, that was one of the ways that we really started taking control of thermal management. Additionally, in 2021, we expanded our capabilities of asymmetric injections so fueling three cylinders at a different rate, basically creating an artificial load on the engine is also another way that we’re able to really send more temperature down the aftertreatment system whenever it wouldn’t normally be doing so under normal operating conditions. So a lot of those things were enablements to having great control of the temperatures going down there, like I’ve said maybe a couple times already, but to prevent us from having to run as long of a race as maybe what some other folks need to do. If you think about, and you mentioned it early on, that everyone had the regulations and how you go about it is going to be different from everybody. So through the announcements you’ve seen so far, I think just about all the manufacturers are doing it a little bit differently. And one of the big things for us is that we’ve been putting out engines that were exceeding NOx requirements for a number of years now. So it essentially was like that we didn’t have as long of a race to run as what maybe some other manufacturers did out there.
Jamie Irvine
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We’re back from our break. Make sure you go and check out the links in our show notes to all of our sponsors. OK, let’s get back to this episode.
I think when people face change, they always have some of the same core concerns, right? One of them would be dependability. But of course, another big concern, especially right now we’re recording in April of 2026, fuel prices are very high again. So how did are changes that are coming in this new engine platform predicted to affect fuel economy?
Mike Young
Sure. So it’ll really impact each fleet operator a little bit differently. And it’s going to come down to how you operate and how you run. I know that’s the case for people already today. But one of the things that we really set up to design the engine to do was to help offset the downsides of having stricter emission controls. So with new emissions and with our updated system, we will be increasing the amount of DEF that’s consumed. Not a terrible amount. It’s going to go from about 5 gallons for every 100 gallons of diesel you burn today up to right about 8 gallons of DEF for every 100 gallons of diesel. And of course, that’s also subject to application and how everyone runs. So we have that as one factor into it. And then from the other side, we made a number of changes around the engine to help offset that. So we expect most people to be running more neutral as terms of their efficiency versus today and it’s really going to come down to how they operate. For overall driving efficiency, we expect it to be a couple percentage points improved over what people have today, but if they are on the low end of idling, so if they’re idling 10, 15% of the time, they’re probably going to see really good fuel economy improvements. If they’re on the camp of idling in that north of 30%, it could be even a detriment. So it really is going to depend on how people are operating their trucks. And a lot of that comes down to the fact that our NOx systems are really great today whenever you’re driving at speed. So in many instances, while a truck is running down the road, there could be 0 NOx being produced by that engine. So not really any work for the aftertreatment that it’s needing to be doing. But the areas that these regulations kind of hit were cleaning up NOx emissions where they’re at their worst, which is whenever the systems are extremely cold. And that happens when you first start up the truck or whenever you’re idling it for long periods of times. So if you get into some of those characteristics where we have to do more work on the aftertreatment side to reduce those emissions, that’s where some of those offsets that’s made by fuel economy improvements may not have a net result that’s an overall improvement. So it’s really going to depend on how people operate. The conditions, even if they run in extremely cold ambient temperatures, could have some impacts as well.
Jamie Irvine
Great. So all of our friends in the Great White North get to experience that for a few months out of the year. When it comes to the maintenance side of this, and I’m thinking also from the parts perspective, it doesn’t sound like there’s going to be a lot of changes or a great need of additional training. It sounds like there’s just a couple extra components in the system.
Mike Young
So there will be a number of parts changes, so don’t want to mislead that. But when you look at the engine from the outside, it’s most likely going to look about the same to most people. I’m sure the technicians are going to notice things right away. They’ll probably be able to notice dozens of things that are a little bit different. But from an overall visual, it’s going to really look the same. I would say probably the biggest thing that stood out to me is that we’re changing our fuel system. So today we’re a fuel lubricated fuel pump and we’re moving away from that and moving over to an oil lubricated fuel pump. So one of the first things that people are likely going to notice is that as they check a fuel filter, it’s going to be black and it’s not something that people are going to be used to. We went through this with engines we’ve had in the past and it’s caused some folks to bring trucks in for service when they weren’t needing to be brought in. It was totally normal operating conditions. And then I would say one of the other biggest things that are standing out with our fuel system change is that we’re moving from amplified fuel injectors to high pressure at the rail. So high pressure directly from the pump. So today, I had the numbers kind of in front of me, make sure to say them. Today, our fuel system uses about 17,000 pounds per square inch of fuel pressure, and it’s going to go up to north of 35,000 pounds. So high pressure fuel lines. So as folks are working on these fuel systems, take note of what engine you’re working on. It’s going to be high pressurized lines right there so make sure to follow all the guidance that’s written within the maintenance manuals. Additionally, the fuel lines are one-time use. So that’s some other changes to look out for.
Jamie Irvine
Well, I’m glad that you listed those changes because obviously, like when these trucks are new and they’re coming back to the dealers, they’re going to have all the breakdowns and the notifications. But once these trucks get a few years older, it’s really important for the technicians and the parts people that are working on the independent service side of the business to understand those differences. And one of the great things about podcasts, they have a very long shelf life. So I’ve had people find these episodes, you know, 2, 3, 4, 5 years ago, and they’re listening to them today. So this will be relevant for that side of the service channel in a few years. So I’m glad you listed those. So with these plan changes in the engine platform, I was kind of curious how that works from the truck manufacturer’s perspective. Like you have to prepare your dealers for having these models on the floor, but then you also have to work out the parts supplier and the, you know, how that’s all going to work. So will you notify the dealers of recommended parts that they should now put in stock once these trucks start rolling off the showroom floor?
Mike Young
Absolutely. And all that work is already going on. I know that our colleagues over in the service groups are making those lists now. And then we’re going to start building some of these engines as what we call them as like demonstrator units or tryouts that were actually run down the line. We’ve already gotten a couple dozen of them that have been pre-built with prototype parts, but we’re going to start running them down the line and putting them in customer trucks here over the next month or so. And then as we start to roll them out on a broader network, then there’s a whole service plan that’s going to get rolled out to everybody. So at first it’s going to focus in on the few customers that will start getting them into their fleets, but then it’s going to be a much broader rollout to the entire network.
Jamie Irvine
Yeah, and if I’m not mistaken, you’ve been testing this stuff for a long time, right? Like these kinds of major engine changes, for people who maybe don’t understand the amount of lead up time that’s required, you’ve probably had prototypes out in the field and put hundreds of thousands, if not millions of miles already on your testing units. Would that be a fair assumption?
Mike Young
It absolutely is. So I know that we have right around three dozen engines running in trucks right now. So it’s what we’ve just had just on our own test cycles. I believe that we’re hitting our third year of summer and winter tests, where they go out and run through the desert and get up the hottest temperatures is what they can get to, and then they’ll go up and run way up north and test them out in those environments as well. And I believe that we’re also projected to hit about 8 million miles in real world driving before we actually launched the engines.
Jamie Irvine
Yeah, I’m pretty sure I saw one of your test trucks in a shop once because I was walking through the shop and this bay was kind of, the truck was closed off you couldn’t really tell. There was things kind of hidden. And I thought to myself, I’m like, oh, that’s definitely one of those prototype trucks. It’s pretty cool. But yeah, there’s a lot of work that goes into preparing for such a major change. When I think about what you talked about when we were talking about fuel economy. Talk to me about who kind of benefits the most from these changes, because it sounds to me like there may be an advantage for over the road versus more vocational applications, but maybe I’ve got that wrong.
Mike Young
No, there’s always going to be pockets that may impact people a little bit differently. Some of the things that have, and I can probably talk about both sides of this, but some of the things that we learned from vocational applications is going to benefit the line haul side of it because we’ve had a technology called a thermal control valve on our DD13 for a number of years now. And we put that on those engines because it’s our leading vocational engine. And those are the ones that are already in high idle applications. So this thermal control valve is essentially something that sits right behind the turbocharger, and it articulates to put an artificial load on the engine and send more heat down the aftertreatment system. One of the most important things we’re able to do is to keep that system hot. And we found that we’re able to really heat up the engines a lot faster and able to improve aftertreatment reliability over time. And that’s the technology we’re taking from our vocational applications and bringing it over to the highway side because it’s really essentially eliminated the need for doing park regenerations of the system. So it’s been a great improvement for that. Additionally, if we kind of break down things that are important to different sides of the segments or speak a little bit about line haul, long haul, Overall, we’re adding new engine ratings to our DD15 that’s going to enable them to get up to higher torque limits to improve down speeding performance, to get in some of those ratios that maybe hasn’t worked for some of those applications in the past. So improving overall performance from that standpoint. And some of the major things that our vocational customers talk to us about is making sure that we’re able to package this new technology in a way that works for them. That was one of the areas that being able to package this new pre-SCR system right on top of what we already have. We’re not changing ground clearance, we’re not adding to back of cab or forcing them to change body equipment designs would’ve been a major switch up for them. So we’ve gotten a lot of benefits that really affect every side the most or every side, I would say in areas that they look for. So additionally, just to speak a little bit more about on vocational side, it’s not always the most important thing that they’re improving overall efficiencies or that they’re getting the most fuel economy out of those trucks, it’s not always what’s important to them, but we still work to make sure that the engine is getting the most efficiency or the most energy out of the fuel that’s being consumed because any fuel that’s going down to the the system is hydrocarbons, is going to be detrimental to the overall system. So it’s important for us still, even on the vocational side, to improve the efficiency of these engines, because anything that you don’t send down to the aftertreatment system, it doesn’t have to clean up. So there’s positives for about everywhere that we put these engines.
Jamie Irvine
I kind of thought of it, but I didn’t mention it before. When you were talking about all the road testing that you’ve done, we had an engineer on the show that was a parts manufacturer, but they were talking about how they approach what they call a five season test, meaning like you got to get through all four seasons plus one to make sure there isn’t any unexpected things when they move into that second year. And I think when you’re testing, obviously, yeah, you’re looking at your wide range of different customers and their needs. And I like the fact that with the Gen. 6, you have the benefit of being able to look back on all of the use cases of all of your different customers who are using the engines in different applications. You’ve been able to learn so much and apply those. That’s one of the advantages, I guess, of an evolution of an engine platform as opposed to bringing out a brand new one because you can look retroactively and take those learnings and move them forward. So sounds to me like customers are able to pick the right engine for the application and that they should have a lot of success with this new platform or this evolution of an existing platform.
Mike Young
Yeah, I believe so. This is something that the rules have kind of had some uncertainty around them the past couple of years with things have been maybe a little bit confusing as statements that’s been out there. But this is things that we’ve been working on close to 10 years now, whenever these programs started. And we work off of what we expected them to be and never slow down. And we always expected diesel to remain a dominant fuel source well into the future now. So we’ve been putting a lot of effort into making sure that these engines are as transparent of an impact of fleet’s operations as well as possible to be. Because the things that are important is that the truck gets on and as the operator gets in the truck, that it turns on and runs and does the job that needed to do. We’re trying to take as many of these emissions related changes, off the front burner.
Jamie Irvine
Yeah, there’s been so much dramatic change in the world over the last six, seven years. And it definitely has flexed all of our resiliency and adaptability muscles for sure. Let me ask you in closing, if there’s just one thing you want people to remember about today’s conversation, what’s that one thing?
Mike Young
We designed these engines knowing that emissions were a large factor and knowing this is going to be the biggest emission change in 17 years. We wanted to make sure that we’re doing it in a way that is able to improve efficiency for folks, meet the emissions requirements using simpler technology. Also, every time we do an engine program, this is not cheap for anything and it’s a lot of time and effort. We found ways to improve overall performance. And then any time we do this, we also want to make sure that we’re attacking reliability and really improving the experience that everyone has to overcome challenges that come with running trucks and having them run through millions of cycles of engine and reducing those impacts that maybe they have. So using a lot of the systems that we have, we found many ways to improve the experience for folks while reducing the impact from the largest regulation we’ve had in, like I said, nearly 20 years now.
Jamie Irvine
You’ve been listening to The Heavy Duty Parts Report. I’m your host, Jamie Irvine. We’ve been speaking with Mike Young, Powertrain and Safety Product Marketing Manager at Daimler Truck. To learn more about Daimler Truck, go to daimlertruck.com. Links are in the show notes. Mike, thank you so much for being on The Heavy Duty Parts Report. I really appreciate it.
Mike Young
Thank you for having me. Appreciate it.
Jamie Irvine
And thank you for listening or watching right to the very end. If you haven’t already, I’d like you to subscribe to the show, follow the show. That way you won’t miss any of these great conversations that we are having with industry experts and the manufacturers who both make the trucks and the components that we are responsible for putting on and keeping these trucks and trailers rolling. As always, I want to encourage each and every one of you to be heavy-duty.
