Turbo failures, EGR issues, glow plugs eating, cylinders, DPF problems, radiator leaks now with the predecessor of this engine being the 6.4 L Power Stroke, which was also a little bit of a disaster. It looked like Ford had also hit the bed with this 6.7 L Power,Stroke, welcome back, I’m Alex. We got the old behind me, but not for long.
You guys ask for it. We’Re ranking the heavy duty diesel engines from best to worst in the segment and I’ll, give you my opinion as a diesel mechanic for whatever that’s worth as to why or where I slotted each engine on my list now for a little bit of a Shameless plug. We are approaching 100,000 subscribers on this channel. So if you like stuff like this, please consider subscribing really helps me out and it helps the channel out two things before we get our first diesel engine in the shop. A couple weeks ago, I ranked all the 1500 engines and, in my opinion, the discrepancy between the best engine and the worst engine was pretty significant, whereas with the diesel engines in the HD truck segment, I feel like they are much much closer and you could make A valid argument for each engine being your number one engine and you wouldn’t necessarily be wrong.
So just keep that in mind. Secondly, we will not be ranking the high output power stroke diesel engine today for a couple of reasons: firstly, because it’s literally mechanically identical to the standard output. 6.7 L Power Stroke aside from two items: it has a slightly different turbo housing and the exhaust manifolds are stainless steel other than that those two engines, the standard and the high output Power Stroke are mechanically identical and I’ve also never actually driven a high output Power. Stroke so I don’t really think that’s fair to rank it, starting at the bottom and unfort.
Fortunately, someone has to be here. We have the standard output, 6.7 L, cumin, turbo diesel. We have a massive asterisk with this diesel engine, because in 2025 is releasing a significantly upgraded engine which is about to roll off the factory lines. However, those 2025 engines are not really ready for sale yet so technically, if I was looking to buy a diesel engine today, this would still be one of my op options, which is why we ranked it at number four.
Now, if You’ asked me this question a couple years ago, when I started the channel, I would have said hands down the 6
7, L cumin is my number one option. I work closely with the commercial grade: ISB 67 cumin and those engines they take abuse pretty darn well and they just keep on going today. However, it’s a little bit of a different story with some pretty well documented engine issues with this Comins engine as well as now having driven and towed all of the diesel engine in the segment under load. It gives me a pretty good perspective as to why I’m just not as high on this standard output cumin engine as I used to be the first reason why this engine finds itself on the bottom of my list is because of the lifter failures. This engine is experiencing.
I’Ve talked about it a number of times on the channel, but in 2019, when last updated this engine they switched to a hydraulic roller, lifter, ditching, the rather simpler flat taet style lifter and unfortunately, the new hydraulic roll lifter has turned out to be A weak point in this engine other issues that I’ve personally seen with these cumins engine include your turbo vgt actuator, failing not an easy job, not cheap either the coolant and oil lines going to your whol set turbo for whatever reason up here in this climate just Seem to get pretty rotten, and, lastly, is the EGR valve seems to get full or clogged with soot, pretty frequently and it’ll, throw a bunch of check engine lights or the EGR Val will just outright fail. Speaking of EGR emission issues are pretty much par for the course across all engines of the diesel segment, but there is one thing unique about this cumin engine and it is how it performs a regen. Now a regen for anyone who doesn’t know is when there’s two much soot built up in the DPF and it has to be burned off. Typically, what we see is raw diesel fuel actually injected right into the DPF or right before the DPF. It gets super hot clears that soot out and you move on with your life.
This engine, however, does not directly spray diesel into the dpfs. This engine instead uses all six injectors and sprays diesel fuel into the engine during the exhaust stroke and it gets pushed out of the engine into the exhaust down into the DPF to be then burned during the regen process. And there’s a couple things that I don’t really like about that. First, you run the risk of potentially washing down your cylinder walls. Secondly, you could make the argument that potentially going to build up some more carbon or sludge on the exhaust system, as well as because you’re pushing that raw fuel out through those components.
The main problem, however, I have with this style of regen, is diluting your oil with fuel trucks that are regening somewhat frequently are going to have a greater possibility of fuel diluting their oil because, as you’re spraying, that raw fuel into the engine during the exhaust stroke, Some of that fuel will make its way past the piston ring and find its way into your oil and, if you’re not changing your oil on a regular basis, you run the risk of potentially damaging some engine components. Usually the canary in the coal mine is your turbo. Those bearings will see the first sign of where, if there is any major fuel dilution in your oil now to add some fuel to the fire, no pun intended these 2019 cin engines, for whatever reason, there’s a ton of people complaining that they regen extremely frequently. Sometimes every 100 miles, in my opinion, a diesel engine should regen, maybe once or twice every th000 miles. So if, if your cummin engine is regening very frequently, make sure that you are changing your oil, nice and frequently because odds are, you will have some fuel diluting that oil, which can create a lot of problems?
Here’S a really interesting post about this topic. This fell has a 2022 C engine and his truck can’t go more than 100 miles without it regening, and he changes oil at 12,000 Mi, which is actually below the Comm, recommended oil change interval. He sent out a sample to be tested. The truck was almost four quarts over full of oil because well there’s a lot of fuel in it. Anyways check out his results.
Almost 10 % of the oil was diluted with fuel, which is severe. It’S it’s it’s not great, and if I was a betting man, I would bet his bearings on that engine have lost some life because, with that much fuel in the oil, the oil is no longer the same viscosity to properly protect the engine and well, as this Po most points out, even if the gentleman changes, oil at say, 6,000, Mi or half the distance, his oil would still have almost 5 % fuel dilution, which is well above what you want. So moral of the story make sure you’re changing your oil frequently. If your truck is regening frequently, both GM and Ford, directly spray diesel into their DPF, even Detroit Diesel, even the bigger cumin engines that I work on, they all spray diesel directly into the DPF, and you just avoid potential fuel dilution. Another major complaint with this engine is the grid heater nut falling off and dropping into the engine.
If you would focus so on the back side of this right here, underneath the intake plate, there’s a nut that sometimes rots off falls into the intake and takes out the number six cylinder. It’S been an issue for a long time on these 67 commment going back. All the way to like 2007 when this engine was first released now in 2025, cumin has finally address this. The new engines no longer have a heater grid system. They’Ll have glow plugs, so this issue will finally be put to bed.
Now. I’Ve actually been speaking with banks performance and they make a very interesting product. It’S called the banks, monster ram and it eliminates that intake heater grid and the possibility of that nut, falling down and taking out your engine. It also increases your air flow and it’s a pretty cool product. I have no affiliation with this product as of yet but seems like people really like these things, not necessarily cheap, but it will 100 % eliminate the possibility of that heater grid nut taking out your engine.
I think the common name carries a ton of weight because of the previous bulletproof engines that they have produced and put into these Ram trucks, but in 2019 I would argue that they sort of stepped away from the tradition of putting a commercial-based ISB 67 cumins engine. In one of these pickup trucks and they sort of focused more on performance and weight savings rather than reliability and long longevity, I think that may have bitten them a little bit in the butt looking at Power. This standard output, 67 commin, is not that powerful. In comparison to the competition, this engine’s putting down 370 horsepower 850 pound feet of torque, which is significantly less than the competition like I mentioned, and when I had this thing on my Towing Loop paired with that, rather subpar sixspeed transmission. It made for a rather weak, showing I do still really like the 67 Commons.
The inline 6 design is barnon the best design for a diesel engine. There’S a reason why? Just about every single semi- running down the road today is running an inline 6 diesel engine because it is the best. So I have very high hopes for the new 2025 cumin engine with a little bit more power, some updated components going back to that cast iron block, hopefully pushing this engine further up the list, but as for the 2024 standard output, 67 cumins. For all those reasons I mentioned, it finds its way at the bottom of my list.
All right moving along here quickly at number three is the high output cumins turbo diesel, and I know I know these engines are on their way out but hear me out guys because since the new 2025 cins are on their way, there’s probably going to be some Pretty damn good deals on these high output engines. The high output commment engine is a slightly different engine than this standard output. We get a lower compression ratio, 16.2 to1 versus 19 to1. We get different Pistons, bigger valves, different intake and exhaust manifolds different injectors, as well as a bigger turbo to give that high output Comm engine all that extra power.
It’S putting down 420 horsepower 1,75 lb feet of torque 31 PSI of boost and we’re at 120 km. An hour, so this thing can definitely pull. However, the high output engine is still based upon the standard 67 cumin engine platform. So, in my opinion, I would still be concerned about potential valve train issues with those lifters regen problems. We get the same style of vgt Turbo actuator, which I’ve seen multiple fail.
We get the same EGR valve that just seems to be always be clogged up with soot, thring check, engine lights or just outright failing, like I mentioned, and the last thing that really bugged me is that the high output commin is only available on the 3500 platform. So, for all those reasons, despite the high output, putting down a lot of power, it falls to number three on my list moving up to number two on our list, and this was a tough decision. I do actually like all four of these engines, but we have the 6.6 L Duramax Diesel. We got ourselves a very, very nice, looking 3500 High Country in the shop today, this 6.
L Duramax the l5p made its debut in 2017 and was pretty darn good right from the GetGo and that’s exactly what GM needed from this engine, because the previous Duramax, the Lml was a bit of a disaster. If I’m going to be honest with this l5p Duram GM put their money where their mouth is and they built a pretty darn good engine. Gm threw the Bosch fuel system along with their cp4 fuel pump right in the bin, and they replaced it with a Denso fuel system. By all accounts, it has been a pretty successful replacement. One of the biggest problems with that previous Duramax diesel engine was that Bosch fuel system, and I like that GM just completely scrapped it and started fresh in 2024 GM updated the l5p Duramax platform, giving it a little bit more power.
This engine is now pushing 470 horsepower 975 LBT of torque, and when I towed with this Engine, with my 14,000lb trailer going down the highway, I was thoroughly impressed with the power output. This thing has Duramax, I hate to say it, but I’m kind of liking. This truck I’m kind of liking it it’s pulling this load very well. The engine braking is awesome. Awesome, it’s the low-end power.
Is there where I didn’t think it would be. The 6.7 L Power Stroke, which has more power on paper. It felt pretty neck and neck, which is something I wasn’t actually expecting with this Duramax Diesel, so plenty of power. Another big thing with this update is GM fixed, their injector connector problems, which was one of the biggest issues that plagued this engine from 2017.
Another big issue which I’ve talked about at length on this channel is the map sensor on these durac diesels. They just seem to get clogged up with soot very very easily. Again, it’s a extremely simple repair and I recommend everyone pulls it out. Every oil change and just clean it off it takes literally 3 seconds. I made a whole separate video explaining how to remove your map sensor, how to clean it properly.
So, if you’re more interested I’ll put that video down below in the description, other complaints are failed. Knx sensors, as well as DEA or diesel exhaust system issues, and if I’m going to be completely honest, noock, sensors or diesel exhaust system issues are just part of the course with any diesel. Another major discussion in terms of issues with these Duramax diesels, including the l5p, is the failing, crankshafts or snpp and crankshafts, and from the research I’ve done. I’Ve gone down to my local dealership, spoken to the service department, scoured the old interwebs, and it just it does not seem like the l5p Duramaxes suffer from that that issue that the previous generation of Duramaxes did like the LML um. Those earlier Duramaxes certainly did have potential problems with crankshafts, but from my understanding, if you keep this engine running stock, it really should not be a problem, so we have some very good power.
We got some really good reliability emissions aside, but there are a couple things that bug me about this Duramax Diesel engine’s design, and that’s why I’ve had it fall to number two on my list. The first thing is that this engine is an over Square engine, meaning that the bore of the cylinders are actually bigger than the stroke, and this is a V8 engine very typical of a v configuration to have an over Square engine. But what that does is it leaves us with a very short stroke. This is the only diesel engine in the segment with a stroke shorter than 4 in and ideally on, a diesel engine, the larger the stroke, the better, because you get a larger crank, though, which means the engine can produce torque, naturally very well, as well as down Low in the RPM band, so the Border stroke ratio on this engine, in my opinion, is just really not that favorable for torque generation. Another design element – I don’t necessarily like with the Duramax – is the use of straight connecting rods versus offset connecting rods.
Both the cumin and the power stroke use offset connecting rods and what offset connecting rods are really good for is helping in the generation of torque. Essentially, what it does is. It allows your connecting rod to be at 90 at Peak cylinder pressure and transfer as much torque as possible down to the crankshaft, where Straight connecting rods at Peak cylinder pressures are on a little bit of an angle. So you don’t get that same torque generation down to the crankshaft, as you would with an offset connecting rods, and I would love to see Duramax be able to use an offset connecting rod. I think it would really help in torque generation as well continuing on with connecting rods.
They are the single component that takes the most force or abuse in an internal combustion engine, which is why a lot of Manufacturers will op to go with fully forged steel connecting rods to take all that pressure of that piston flying up and down and what’s interesting, Is GM went with a powdered metal connecting rod, something I was not expecting to see out of a very powerful diesel engine where both the cumins and the power stroke both have fully forged steel connecting rods? It’S very interesting, potentially a weak point, and I’m not saying this engine is having connecting rod issues because it’s not, but I would have loved to have seen GM go with a fully forged, connecting rod as well as a fully forged rotating assembly to give this engine. As much strength as possible, something that my number one engine does so, for those reasons, that’s why this Duramax Diesel is number two on my list. It’S a nice, reliable engine makes plent plenty of power, but I feel like the design or the workings of the engine is not necessarily optimal for torque generation, which is why I ranked it at number two all right number, one on the list. You guys guessed it, it is the 6
7 L power stroke diesel also known as the Scorpion underneath the hood here we got a very powerful engine.
This thing’s putting down 475 horsep our 1,50 lb feet of torque, and this is the only engine with a fully forged rotating assembly. Forg crankshaft forg connecting rod fully forged steel Pistons. This 6.7 L Powerstroke made its debut in 2011 and boy. Oh boy, was it not pretty?
The first generation of this engine 2011 to 2014, was littered with problems, turbo failures, EGR issues, glow plugs eating, cylinders, ppf problems, radiator leaks now with the predecessor of this engine being the 6.4 L Power Stroke, which was also a little bit of a disaster. It looked like Ford had also, the bed with this 6.7 L Powerstroke, but long behold, Ford did Iron this 6.7 L Power Stroke out to what it is today like the Duramax Diesel.
This Powerstroke engine is a V8 configured unit, not necessarily the ideal diesel engine. In my opinion, I still think think an inline 6 is superior, but I really really like what Ford has done with this platform. So, first off we have a hot Center engine, meaning that the exhaust gases are actually coming in between the banks into the center of the engine and her intakes are actually on the outside of the banks, completely opposite of what you’d normally see on a V8 engine. Ford says this helps reduce pumping loss as well as heat loss to the turbo, because the turbo sits right in the center of the banks and if our exhaust piping is all going into to the center of the banks as well, the exhaust gases get to travel Less distance to get to the turbo we’re going to lose less energy and that energy gain can be shoved right back down the throat of this engine, making more power. One downside of this, in my opinion, is the piping or the Spaghetti Factory that we get under the hood here with this power stroke.
Another design feature that I like about this engine is how long of a stroke it has for a V8 engine. In fact, this V8 engine isn’t undersquare engine, something once again, we don’t really see with a V configuration engine. In fact, the board stroke ratio is 0
92, which is a very heavy undersquare engine, our 67 cumin, for example, which has a massive stroke, has a border stroke ratio of 0.86, whereas the 6.6 L Duramax Diesel has a border stroke ratio of 1.
5, something that we typically see with a V8 engine. So I really like that Ford has purposely designed this V8 engine to have a very large stroke because, as I just mentioned with the Duramax Diesel, the longer the stroke of a diesel engine, the more Advantage it has to creating torque and well. This 6.7 L Power Stroke is a bit of a torque monster. Alongside with the very nice border, stroke ratio, this engine has for maximum torque generation.
We also get fully forged offset connecting rods, which is going to further help in the torque generation department. So, despite this engine being a V8 engine, something which I would say is not the most advantageous engine design for diesels. I really like the way Ford has gone about designing this V8 to make it rather advantageous when it comes to torque generation in terms of towing, with this 6
7 L Power Stroke it’s pretty much topnotch, he pulls hard and heavy and well with onp paper power figures like what this engine has. It should be what you expect expect and if you do tow with this engine, you’re probably going to be very happy. One of my biggest complaints with the 6.
L Power Stroke is the use of the cp4 Bosch fuel pump they’ve been using it since its debut in 2011 and stuck with it, despite the cp4 fuel pump having a reputation of blowing up and spreading metal throughout the Fuel system making a very costly repair, both GM and RAM, have used and tried the BOS C4 fuel pump with not very much success. In fact, there were a lot of failures. The power stroke, however, does seem to have less cp4 fuel pump failures than both GM and RAM did, for whatever reason so take that with a grain of salt, a benefit of the cp4 fuel pump is it can generate very, very high fuel pressures. This 6.7 L Power Stroke is running up to, I think 36,000 PSI of injection pressure, which is very high and it helps with atomization, helps with lowering emiss and creating more power.
So there are pros and cons, but I still feel like the cp4 is more of a con than a pro. So there you go. That’S my opinion of diesel engines currently in the segment. If I was going to buy one tomorrow, I do think you could make a very valid argument for any one of those engines to be your number one choice, because at the end of the day I do think they’re all pretty decent engines and well. Let me know what you think of my opinion.
I look forward to hearing your arguments as to why or why not. You agree with me down in the comments, but if you did like the video, don’t forget to leave that thumbs up and, like I said at the beginning of the video, if you like stuff like this, we’re on the march to 100,000 subscribers with this channel, pretty Big feat, so don’t forget to hit that subscribe button. If you want to help support the channel help support me I’d very much appreciate it, but anyways enough of me we’ll see in the next freaking video