Poor fuel mileage on 2024 Duramax

MesaRat · September 5, 2023

I picked up a 2024 Silverado 2500 LTZ Duramax about 3 weeks ago and my fuel economy is averaging under 15mpg over the first 3 tanks, no towing. I drive 85% rural highways (55 mph), 15% city, don't hot rod the truck, and have owned 5 HD diesel trucks. I have 1500 miles on the truck. My trade in was a 2020 Silverado 3500 Duramax and I rarely got below 18mpg (sometimes close to 20). My other HDs were Fords and they never fell below 17 mpg.

I asked the dealer if there are any bulletins (regen or fuel mileage) and they said no. It does seem to be regen'ng more than the other truck but I am not certain.

Any insight or help is appreciated.

Thanks

MTU Alum · September 6, 2023

Sounds pretty typical. It will probably pick up a little but I wouldn't expect more than 16 to 16.5 on two lane with stop and go.

There was a change late in 2020 model year where the engine Regens more frequently to help prevent cracking DPFs. The mileage went down with regen frequency.

#iworkforGM

MesaRat · September 6, 2023

20 hours ago, MTU Alum said:

Sounds pretty typical. It will probably pick up a little but I wouldn't expect more than 16 to 16.5 on two lane with stop and go.

There was a change late in 2020 model year where the engine Regens more frequently to help prevent cracking DPFs. The mileage went down with regen frequency.

#iworkforGM

Thanks. The change to the regen frequency might explain it.

Crazy Canuck · September 6, 2023

My '24 with 2500kms is averaging 14.957 mpg and it sounds like our driving is reasonably similar. My '22 was 14.820 over its 12k km that I owned it and my '21 was slightly better at 15.314 mpg over a similar life if me owning it. The '22 ran through noticeably more DEF than my '21. So far, I would say the '24 Regens a bit less than the '22 but still early in its life.

Lhpnick · September 23, 2023

I have a 23 2500hd Ltz Duramax and fuel mileage is awful. Same as you under 15. Driving style similar as well. Have 25,000 miles on it now and still the same as when I got it in January. Once In a while it will jump upto into 17 and 20 range for a day or 2 then drop back to under 15

madweazl · September 23, 2023

I was on rural two lanes the other day and was pretty happy averaging 18.5mpg (reported from the cluster) over the course of 100 miles with 80% rural roads (typically 45-55mph), 10% city, and 10% highway (flow of traffic was about 70mph).

gemarsh · September 23, 2023

https://gmauthority.com/blog/2023/09/2024-chevy-silverado-hd-gmc-sierra-hd-recalled-for-faulty-fuel-injector-flow-rate/

MesaRat · September 24, 2023

On 9/23/2023 at 7:06 AM, gemarsh said:

https://gmauthority.com/blog/2023/09/2024-chevy-silverado-hd-gmc-sierra-hd-recalled-for-faulty-fuel-injector-flow-rate/

Thanks. I'm curious to see if my truck is one of the ones identified. I do get on occasion a rough idle but thought is was just characteristic of the engine.

ducky911 · September 24, 2023

My 2024 2500hd Duramax ultimate got 17mpg on first tank...highway, around town and idling in driveway as i played with it.

First 100 miles it was at 22mpg. than hills and regen happened, I felt like I had two regens on the first tank, not sure. Truck seems more sensitive to wind, hills, and acceleration.

Funny I came here looking to improve my mpg.....2018 always got better than 18 even when new and increased to 19+ on full tanks.

MesaRat · September 27, 2023

Has anyone been able to get the dealer to confirm recall #N232415860 for their truck or had the recall performed? The local dealer says mine isn't in the system yet and the system is having trouble.

MaxDura · September 30, 2023

On 9/26/2023 at 8:04 PM, MesaRat said:

Has anyone been able to get the dealer to confirm recall #N232415860 for their truck or had the recall performed? The local dealer says mine isn't in the system yet and the system is having trouble.

I have an early 24 with poor mpg that I expect to be included. I also have the ability to see open recalls for my truck and can confirm its not in the system yet. I too concluded that the system is FUBAR. Appears to me that they got the cart ahead of the horse in regards to announcing a recall without 1st identifying and tagging the affected vehicle population.

ducky911 · October 7, 2023

First towing....travel trailer 30' 9200 lbs 200 miles freeway , no wind, bunch of two way road and some up and down hills.. 11.9 mpg

I think the best my 2018 did was 13mpg

so happy enough. cameras are amazing!

Edited October 7, 2023 by ducky911
spelling

clongtine · October 9, 2023

I had this recall completed on mine and can confirm the truck does idle smoother now. I have not looked at fuel economy to see if there was a change yet. The dealer did say the update process was a pain as they had to scan the barcode on each injector one by one to complete the ECM update.

Cory Stewart · October 9, 2023

My 2024 3500 dually gets terrible milage compared to my 2020 at4, I tow a toy hauler alot it is 47 feet and weighs 22000 pounds, I can go through an entire tank of Def in 100 miles. I liked my 2020 so much I kept it. I average 12 towing the trailer on my 2020 and barley use any Def, I average 6 in my new truck and have to carry 4 boxes of Def with me whenever I go out. My dealer did an ecm update and it got better, but just went out last weekend and again used a full tank of Def with a tank of fuel. Something is definitely off.

MesaRat · October 14, 2023

After some back and forth with the dealer and calling GM, it appears this recall is very limited (about 900 VINs according to GM). Dealer did confirm that my ECM software is current version.

I started using Stanadyne a few tanks back and my regen's seem much shorter now and getting low 16's. I did let GM know there is no reason that the same driver and habits in almost identical trucks should get 15-20% less fuel efficiency.

Edited October 14, 2023 by MesaRat
correction