Fuel Mileage

rusmis91

New member
Nov 12, 2025
2
1
3
WV
My 2024 Chevy Duramax is only getting 17.5 mpg. Anyone doing anything to get better than this. Would like to see about 20mpgs. Everything is still stock
 

2004LB7

Super Moderator
Staff member
Dec 15, 2010
8,551
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Norcal
Only???

My lightweight smaller 05 can get 20. Id love to even average 17.5 with my 08. I can do that with highway only, but no way with mixed driving

Not surprised a heavier larger 2024 isn't able to match MPG of the older lighter and smaller trucks
 

NC-smokinlmm

<<<Future tuna killer
May 29, 2011
5,516
590
113
At Da Beach
At what speed? Mine will get 20 mpg under 60 mph. It’s gotten almost 24 mpg at under 50 mph and that was a 50 mile average.
 

Bdsankey

Vendor
Vendor/Sponsor
Feb 1, 2018
4,817
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Larsen, Wisconsin
I'd say that mileage isn't all that bad considering it's an 8k+ lbs brick driving down the road.

What speed, what elevation and what kind of terrain do you live in?
 

GTO_Gregory

New member
Sep 14, 2015
2
0
1
New York
My 2024 isn't very good with fuel mileage: figure 16.5 highway and 13 city.
My 2015 would get 21 highway and 17 city. It had a FASS, a tune, and 35" diameter tires.
It's true, the 8,300 weight of the 2024 doesn't help. But I'll do the same tricks as before, and I'm confident fuel mileage will improve.
 

NC-smokinlmm

<<<Future tuna killer
May 29, 2011
5,516
590
113
At Da Beach
Try adding some of the gold power service, my mileage was down and a couple tanks of the additive brought it right back up. The injectors get clogged up and cause a lot of the problems with emissions equipped trucks.
 

Hambone

Always learning
Jan 24, 2016
591
20
18
Florida
Just went on a road trip and was seeing 22 on the dash with the 50 mile distance avg 72mph
Overall trip was 18.5 on the dash and hand calculated.
I could tell when a regen was happening and watched the mpg drop like a rock.
End of the day we dont buy these for mpg :)

Edit* its a '24 CCSB
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
23,033
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Phoenix Az
Try adding some of the gold power service, my mileage was down and a couple tanks of the additive brought it right back up. The injectors get clogged up and cause a lot of the problems with emissions equipped trucks.

no they dont…
 

TheBac

Why do I keep doing this?
Staff member
Apr 19, 2008
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Mid Michigan
OK kids, stop the arguing. Do I need to pull the truck over? (I AM old enough to be your Dad, remember?) :LOL:

We all know that diesel injectors are not the most reliable things on earth. Its entirely possible the spray patterns are messed up, or they're leaking past their pintles, or one of any number of other issues that can cause shitty mileage. Will cleaning the fuel system with an additive help? Maybe, maybe not....but its always worth the try initially. After that, it just gets expensive.

We also DO know the draconian emissions garbage doesnt help at all. Maybe there's a fault in that system thats causing the issue with the O/P truck. There's sure not enough info in the post to go by to argue about it. Maybe the new Power Service additive can help the emissions stay in good nick for longer. There just isnt enough hard evidence to show it does help yet. Would I discourage its use? No, I wouldnt. Again, its worth the try.

Lastly, we have no idea how the O/P uses his truck, how its driven, or any of a million other things that can cause poor mileage. We cant ignore that.

Bottom line: IMO, anyone who thinks a 7500lbs, 450hp truck is going to get mid-20s or better overall is just fooling themselves, or thinks the DIC reads accurately. Maybe with a refined tune it could, or a with a strong tail wind. But physics usually wins that argument.
 
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Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
23,033
8,045
113
Phoenix Az

Yes, i can read a label too .

Sitting there telling someone your injectors are clogging up and you need a cleaner is bs. Do some diag or have the op actually do the proper diag to know if thats even the issue. Shit like this is why i have customers coming into my shop all the time trying to tell me why they think they know they need “x” to fix it or some other dumbass shop saying “run a cleaner through it, its going to fix it”, they do and then they just caused more issues or didnt do a damn thing and now im showing them how their nox sensor is now poisoned because they didnt follow the proper steps on said label or how their dpf has cold spots during a regen because they “added more” than the recommended amount of additive and plugged the dpf. Put up some actual proof of what it did that is third party based

These injectors are not a VCO where they plug up with shit. We are 20 years newer than that. I have a 15 lml in the shop right now with 400k miles on it, all emissions in tact and injectors are perfectly healthy. Not a single additive used. Ive had plenty of l5p’s come through my shop as well with over 200k and no additives. Not a one had an injector issue. Injector connector, absolutely, injector its self, nope. Does it happen? Probably but nothing near the extent of what some of these companies claim.

Do you know what a leaky injector does to an emission truck, what codes it sets and how the truck acts when it happens? Do you know what a plugged injector does to the emission system, codes it sets and how it acts? Theres a hell of a lot more symptoms than “slight drop in fuel mileage”.

Put up useful facts that back what your stating, not what the label says. We arent banks where we claim we use data to back what we sell only to show half the data behind it that helps marketing, not the other half that says otherwise. This site has always be about the facts, i intend to make sure it stays that way
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
23,033
8,045
113
Phoenix Az
Fact’s actually change over time so have fun with that one. Enjoy your site James won’t be long until it’s just you…

I’m out…

giphy.gif
 

Bdsankey

Vendor
Vendor/Sponsor
Feb 1, 2018
4,817
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Larsen, Wisconsin
I haven't played with DEF/DPF additives myself so my statements here are purely based on theory so take them as that.


Do I think it's possible an additive can help prolong the life of an aftertreatment injector or the aftertreatment itself? Absolutely.

Do I think it's a smoking gun industry that will actually show long term benefits? Ehh, not really. The injector tech (and now injector designs) follow today's fluids where I think that's less of an issue. I think the gains will be single percentage in terms of lifespan not like when we first got VCO injectors.



Again, this is all theory based on what I've seen with injector tech over the years. Most of the vehicles up in my neck of the woods are pre-emissions or have already been removed by someone else and tend to come in for transmissions, CP3 conversions, injectors etc.
 

gmduramax

Shits broke
Jun 12, 2008
4,185
325
83
Nor cal
Try adding some of the gold power service, my mileage was down and a couple tanks of the additive brought it right back up. The injectors get clogged up and cause a lot of the problems with emissions equipped trucks.
Kinda hard to believe an injector will clog up when there’s 30k psi flowing through them, anything making it through the filter will just get blasted to nothing.
 

LB7StillAlive

Member
Nov 27, 2025
54
34
18
Arizona
Those orifices are pretty small, so it wouldn’t take a very large particle, however I agree with your logic. At those presssures I’d imagine it would vaporize all.

It’s an interesting video if you haven’t watched it. It more talks about the benefits of the cetane boost and lubricity added. It’s a cool comparison of what those additives are doing on a practical and scientific level. Perhaps less to do with the DEF system, and more to do with overall health of the moving parts.
 

Durabiopwr

New member
Aug 2, 2025
11
3
3
Eastern washing state
Pretty sure on the 21's and newer they retarded the timing even further to reduce NOx even more. But retarded timing gets crappy fuel econ and makes more soot and regen more often.

My early 2020 enjoys 20mpg driving 60-65 unloaded. But there is an update to address supposedly 'DPF regen temps'. Everybody that has done the update immediately drops 2-3mpg and regen more often. Pretty sure the update retards timing and maybe some other calibration stuff. Nope, mine is fine and still enjoy 807mi distance between regens at 45Kmiles on the rig now.