Fuel efficiency drop in newer models ?

[Sparksalot]

The only way Big Mama could get 28 mpg is if I was going downhill with. 60 mph tailwind and the GM optional sail package was activated. Your 2018 is incredible.

I suspect that is the truth for many.

 

[viven44]

Is your data based on vehicle calculations, or did you manually keep a log with real calculations?
I have logged all fuel consumption for the last 7 or so years. Many times the calculations differ from vehicle data. Many times better than reported, but occasionally, less than. Most less than comparisons were more city than highway driving.

I went and checked back with manual fueling logs... on the suburban, fully loaded closer to 12mpg, and trailer only at 14.7mpg. But the logs aren't exact as well as there is mixed driving between fuel ups....

I'd say all the numbers I've provided above are +/- 1mpg.

 

[Marky Dissod]

Spot the problem
Our 2002 Yukon and our 2024 suburban have the same engine displacement (5.3L)
Our 2002 is just a simple port injected engine and our 2024 has cylinder deactivation and DI fuel system
Our 2002 has a 4L60E and our 2024 has a 10L80E
Our 2002 is more fuel efficient than our 2024 for city AND hwy driving
Our 2002 can tow as much as our 2024

Weigh the '02 & the '24, then do a rough drag area comparison (frontal width & frontal height).
Strongly suspect '24 is heavier and also has worse drag area compared to '02.
(tuning may also play a significant role?)

I've improved my highway MpG by 2-3 by fixing a coroplast sheet to the underbelly.
(Also slows corrosion for much less than chemical underbelly surface treatment.)
'06 NON-Z71 front air dam proven to improve highway MpG, may give you some ideas for your '24?

 

[vcode]

Weigh the '02 & the '24, then do a rough drag area comparison (frontal width & frontal height).
Strongly suspect '24 is heavier and also has worse drag area compared to '02.
(tuning may also play a significant role?)

I've improved my highway MpG by 2-3 by fixing a coroplast sheet to the underbelly.
(Also slows corrosion for much less than chemical underbelly surface treatment.)
'06 NON-Z71 front air dam proven to improve highway MpG, may give you some ideas for your '24?

The 2024 probably weighs 700-800 lbs more and has 70 more HP. EPA ratings for the 2002 are 14/17 vs 15/20 for the 2024. I'm sure acceleration is no contest as well....

 

[Marky Dissod]

The 2024 probably weighs 700-800lb more, and has 70 more PEAK HP.

Since the younger one is heavier, does it also have worse/more drag area?
No one knows with any accuracy how many horse either engine puts out @ 1500RpM or 1750RpM or 2000RpM,
which are far more relevant to highway fuel economy.

EPA ratings for the 2002 are 14/17 vs 15/20 for the 2024. I'm sure acceleration is no contest as well ...

EPA ratings don't sufficiently correlate to real world experience.
City MpG should be tested by cabdrivers in major cities. Highway MpG should be measured @ 55MpH, 60MpH, 65MpH, & 70MpH over at least 30min or more.
Either or both of those would yield more helpfully relevant MpG data for most of us.

 

[vcode]

Since the younger one is heavier, does it also have worse/more drag area?
No one knows with any accuracy how many horse either engine puts out @ 1500RpM or 1750RpM or 2000RpM,
which are far more relevant to highway fuel economy.

EPA ratings don't sufficiently correlate to real world experience.
City MpG should be tested by cabdrivers in major cities. Highway MpG should be measured @ 55MpH, 60MpH, 65MpH, & 70MpH over at least 30min or more.
Either or both of those would yield more helpfully relevant MpG data for most of us.

A more meaningful stat would be HP required to maintain 60 or 70mph. That accounts for drag and drive line losses. Used to see those figures in tests years ago.

 

[viven44]

Fuel efficiency is just about gone with the 10-speeds I swear. Our 6 speed equipped 2018 got significantly better fuel economy, the 2018 and the 2024 are a lot closer in GVWR, etc.

The 10-speeds were probably developed for towing, the 2024 does exceedingly well in towing my car hauler. If only it had leaf springs in the back with a 3/4 ton setup like the old 2500 Suburbans it would be the ultimate rig.

 

[Marky Dissod]

Fuel efficiency is just about gone with the 10-speeds I swear.

Because weight and frontal drag area are more important than how many speeds the transmission has.
Check this post again

Fuel efficiency drop in newer models ?

I get about 32 with the cruise at 60 or so, on level ground. 2022 5.3 Tahoe, 4x4. I am not sure I believe that...you have the distance set at 25 miles, so computer calculating your BEST 25 mile score and your AVG over the last 25 miles driven. Flip the page to the screen on the current drive...

www.tahoeyukonforum.com

You may notice that 10L80's 2nd gear is pretty much 4L60's 1st gear; explains off-the line acceleration from stop.
May also notice that 10L80's 9th gear is pretty much 4L60's 4th gear.

10L80: ... 4.69 ... 2.99 ... 2.15 ... 1.77 ... 1.52 ... 1.28 ... 1.000 ... 0.85 ... 0.69 ... 0.64 (7.32 Spread)
4L60E: . . . . . . .. 3.06 . . . . . . . . . . . 1.63 . . . . . . . . . . 1.000 . . . . . . .. 0.70 (4.43 Spread)

If the 10L80 spends enough / too much time in 9th -
as in, not much / not any time in 10th for whatever reason -
(avoiding Cylinder Confusion, or speeding too fast to be in 10th)
10L80'll get about the same MpG as 4L60 ... minus weight and drag area.
Even more compression and direct injection can't quite make up for a bigger heavier brick.