I’Ve heard a couple Rumblings that the 2024 6.6 L Duramax engine, the second gen l5p in these HD Chevy trucks, are not getting good fuel economy. Well, today, we’re going to take this truck on my fuel economy Loop and see what kind of fuel economy we get in the real world. Welcome back to the channel guys, I’m Alex! Today we are finishing out our Duramax miniseries, with a fuel economy run these big HD trucks do not have a classified or a official fuel economy rating, but diesel engines in theory are more efficient than gasoline engines, and so these big boy engines, big diesels, can surprise People with how efficient they can actually get, although with one exception, these things run passive Regens from time to time, my fuel economy Loop consists of 85 miles of driving with three sections.
We got a City Section country driving section as well as a highway driving section. Ideally, giving us a really nice combined fuel economy score now before we put this thing in drive and get her down to the gas station. What do you guys think this thing will get in terms of combined fuel economy? My guess is 18 m per gallon. We’Ll see and look at that guys, I even got her in miles per gallon for you uh currently sitting at 11.
That’S cuz. We were just Towing 14,000 lb that will improve and obviously will reset our fuel economy at the old gas station. Give me play on V some Chief avatus from 16. We got a full tank diesel just reset our fuel economy, trip meter and uh we’ll hit the road.
Obviously we’ll do the math, the real math. When we get back so don’t you worry. So I Tred to keep the truck at 60 km an hour throughout the city. Obviously, right now we’re stopped, but that is the beauty of City driving. It is very unpredictable and that’s what probably helps to contribute to poor fuel economy than let’s say driving on the highway.
Now, usually, I try and talk about some of the cork. Some of the uh features that an engine has to try and save fuel in the city. Like start, stop technology cylinder deactivation, smaller displacements with turbos, but this is just a big old 6.6 L, Diesel and uh. There really is no tricks up this thing sleeve.
So we’ll just see what kind of fuel economy it gets. One thing I can probably guarantee is happening is we are just filling up this DPF with lots of s? You got to love it. Well, we just left the city. We averaged 15.m
per gallon. According to the computer, anyways, not terrible, that’s kind of actually right where I figured, we would be ideally setting this up for a combined fuel economy of 18 MP gallon, which is my guess we are currently on our country section. Now I got the cruise control set at 56 mph, which is 90 km an hour and uh we’ll see what kind of fuel Eon we can get on our country stretch. The reason why diesel engines are more efficient than gasoline engines is for a number of reasons. The first reason is well because diesel fuel just has more energy in it per liter than gasoline.
That’S number one. The second reason, and probably the most important reason is that diesel engines have a greater thermal efficiency than gasoline engines. Thermal efficiency, meaning how well an engine, can take its fuel energy and transfer it into mechanical energy. A diesel engine is usually around 30 to 35 %. More thermally efficient than a gasoline engine.
Diesel engines have a higher compression ratio and that’s helps give them better thermal efficiencies. This engine right here has a compression ratio of 16 to1 when looking at something like a 53 and a Chevy 1500. That engine has a compression ratio of 11 to1 and while diesel engines are not limited to engine knocking where gasoline engines can only have such a high compression ratio before they start to knock like crazy diesel engines, don’t which gives them higher compression ratios better thermal efficiency And therefore, better fuel economy. Well, we are nearing the end of our country section. We are currently sitting at 20
3 m per gallon, pretty impressive.
Actually again, this is just what the computer’s telling us, so we won’t get uh too antsy about it, but so far, looking pretty good um we’re about to jump on the highway and I’ll catch up with you guys there now. I was just thinking about regen passive regen, so this truck will run a passive regen. It feels like the uh DPF filters are full of soot. We just ran a pretty heavy load down the highway bu roughly 120 miles. So I would imagine the DPF filters are pretty nice and clean, so we’re not going to be running any passive Regens on this run.
I suspect, and I’ll talk more about just a second, that the poor fuel economy reported could be because of more frequent Regens. With these trucks, well it’s time to drop the hammer we’re now on the highway, we’re going to cruise at um 70 mph. Now, usually, when I talk about a turbocharged engine in the gasoline side of things, we normally see a decrease in fuel economy on the highway. At these speeds, just because well it’s going to shove more boost in the engine in order to maintain our speed as well as these Hills. Now I suspect, with this diesel engine, we’re probably not going to see that I think we’re probably going to stay around 20 m per gallon.
I could be wrong. I’Ve been wrong with a couple of predictions with this Duramax so so far in this series, one thing that greatly hurts a Modern Diesel. Engine’S fuel economy is the emission system that comes with these engines. You have your diesel oxidation Catalyst, diesel particulate filters, um, selective catalytic reduction, all of which kind of make it like this engine is trying to blow through a straw to get its exhaust out and well, it’s just not going to help efficiency. I would probably bet that a 20-year-old clapped out Duramax fre emission engine would most likely get better fuel economy than something like this brand new second gen l5p, the biggest increase in fuel economy.
Consumption in these engines, in my opinion, is probably what’s called a passive regen and, as many of you guys probably know with the diesel partic filter, once it gets full of soot, the truck will want to run a regen. Basically, what that does is it gets the particular filters up to a very high temperature and it burns off all that soot and cleans the filters, but in order to do that, you need more fuel and well. That is why a lot of these Modern Diesel engines just are simply not as efficient as pre-emission diesel engines. If I had to guess why people were complaining that newer engines like this Duramax are getting far worse fuel economy than what they’re used to it’s, probably because of the increased regen frequency um emission standards have become Tighter and Tighter and well. It just seems like these modern trucks are regening even more frequently than trucks that were built a little bit earlier.
So, that’s maybe why I would suspect a lot of people are not happy or as happy with the fuel economy they’re getting with these newer Modern Diesel engines. Oh yeah, there is your paper right there, ladies and gentlemen, getting hauled of the mill good old western star. I think I saw Cummins emblem on there, for once I was actually right. We stayed basically exactly where we were when we got on the highway, we’re just about to get off the highway averaging 20.2 m per gallon, we’ll see what that is.
When we get to the gas station 20.3 m per gallon, we will fill this old girl up. All right we’ll let her sit for a second 3 2 one. There we go. That’S all she’s going to take 17.
L exactly well well! Well, we are back in the shop got the official receipt here did some official math, and this is the first truck that has really lied to us on our fuel economy runs this truck said I believe we had 20.3 m to the gallon at the end of Our Loop there turns out, we only had 18
5, MP gallon: it’s pretty big difference actually and don’t don’t know why the computer was so far off butth the math doesn’t lie, so we were actually pretty much right where I predicted. We were about 18 miles to the gallon and if I own this truck big 6.6 L, this thing weighs 8,300 lb.
I would honestly not be too um unhappy with that. Let me know what kind of fuel economy you guys are getting with your newer Duramax engines. So I always say I like to hear from real owners with real world experience with their own trucks um. But if you did like the video, don’t forget to leave that Thumbs Up And as always, if you like cool stuff like this, don’t forget to subscribe, because we’d love to have you on board anyways enough of me, we’ll see you in the next freaking video
