Fuel efficiency drop in newer models ?

WalleyeMikeIII said:

In calm conditions (no wind), flat ground, 65MPH, I routinely get 21-22MPG on highway in my 22 XL Denali. Wind, heavy foot, etc, will decrease it..

Click to expand...

viven44 said:

Hi all,

We just bought a 2024 Suburban Z71 with the 5.3 and 10 speed transmission... now before I go further, I am not very concerned about fuel efficiency (otherwise we wouldn't have bought the vehicle) I am simply making observations and expressing some level of disappointment in engineering decisions that haven't benefited everyone...

Compared to the 2018 with the 5.3 and 6 speed transmission we used to have we are noting that real world fuel efficiency

- in the city is slightly better in the newer model (13mpg vs 15mpg)
- on the highway we are noticing a significant drop in fuel efficiency. On our 2018 if we drove it well we averaged 26-27 mpg whereas on the 2024, we are maxing out at about 18 mpg... (when we had the Range AFM dongle plugged in on the 2018 we still averaged about 24-25mpg...)

The low-end torque was also honestly better with the 2018 with the 6-speed transmission.

The official ratings (from fueleconomy.gov) are definitely supportive of our observations that the outgoing models were better in fuel efficiency.

No change in Tow ratings vs the outgoing model

I loved the 6-speed and it was easy to service and maintain (relatively easily dropping pan, change filter, change fluid, monitor via dipstick). The 10-speed's oil pan is right under the exhaust and looks like both the driver and passenger side manifolds have to be undone to even drop the pan.

I don't see any articles or discussion over this. Being in the engineer profession myself, I am not seeing a better "Figure of merit" with the new technology. Hopefully somebody can educate me on what I am missing.

Click to expand...

Attachments​

• 
  21.2 on all 8 .jpeg
  137.7 KB · Views: 1
• 
  22 with DFM.jpeg
  130.2 KB · Views: 1

Marky Dissod said:

For those that may not fully appreciate it:
Multi-Port Fuel Injection happens during the intake stroke, mixing it with air before compression
Direct Fuel Injection injects fuel into the air during compression.

Point is, DI SHOULD be able to take MORE advantage of higher octane, compared to MPFI.
But if you use 89 or 91 or 93 in your DI V8, it should not only yield better MpG,
but also better Miles per DOLLAR.

Click to expand...

Marky Dissod said:

... DI SHOULD be able to take MORE advantage of higher octane, compared to MPFI.
But if you use 89 or 91 or 93 in your DI V8, it should not only yield better MpG,
but also better Miles per DOLLAR.

Click to expand...

vcode said:

High octane here is totally useless if you don't need it as 93 is currently $1.20/gal more than 87.

Click to expand...

B-train said:

Another thing to add is this: most new engines have a richer running break-in period from new. Based on miles and time. The calibration is set to this to help protect the motor, seat the rings, etc. After 5k you will probably see more realistic numbers.

Click to expand...

viven44 said:

Hi all,

We just bought a 2024 Suburban Z71 with the 5.3 and 10 speed transmission... now before I go further, I am not very concerned about fuel efficiency (otherwise we wouldn't have bought the vehicle) I am simply making observations and expressing some level of disappointment in engineering decisions that haven't benefited everyone...

Compared to the 2018 with the 5.3 and 6 speed transmission we used to have we are noting that real world fuel efficiency

- in the city is slightly better in the newer model (13mpg vs 15mpg)
- on the highway we are noticing a significant drop in fuel efficiency. On our 2018 if we drove it well we averaged 26-27 mpg whereas on the 2024, we are maxing out at about 18 mpg... (when we had the Range AFM dongle plugged in on the 2018 we still averaged about 24-25mpg...)

The low-end torque was also honestly better with the 2018 with the 6-speed transmission.

The official ratings (from fueleconomy.gov) are definitely supportive of our observations that the outgoing models were better in fuel efficiency.

No change in Tow ratings vs the outgoing model

I loved the 6-speed and it was easy to service and maintain (relatively easily dropping pan, change filter, change fluid, monitor via dipstick). The 10-speed's oil pan is right under the exhaust and looks like both the driver and passenger side manifolds have to be undone to even drop the pan.

I don't see any articles or discussion over this. Being in the engineer profession myself, I am not seeing a better "Figure of merit" with the new technology. Hopefully somebody can educate me on what I am missing.

Click to expand...

DocDoug said:

I get about 32 with the cruise at 60 or so, on level ground. 2022 5.3 Tahoe, 4x4.

Click to expand...