Bad mpg?

[petethepug]

A new 5.3L V8 with a 10 SP, direct injection, DFM, running on adaptive cruse and 17.5 mpg on Reg fuel isn’t bad at all. Not sure what rims and tires you’re running or how hard a/c was working.

 

[blanchard7684]

I'm 5000 miles into a '24 suburban z71 with 5.3. I'm not focused on fuel mileage in general. However in testing difference between DFM and DFM disabled (L9) is noticed only about a 1 mpg difference with DFM engaged.

Where I drive it is alot of 75 mph highway, wind, and frequently a lot of hills.

I'm getting 17.5 mpg on average.

The window sticker values don't really reflect real world (75 mph speed limit) driving.

When I go 65 mph for appreciable amount of time I can easily meet and usually exceed the window sticker values.

 

[Marky Dissod]

... window sticker values don't really reflect real world (75MpH speed limit) driving.
When I go 65 mph for appreciable amount of time I can easily meet and usually exceed the window sticker values.

I find it interesting that, after decades of Corporate Average Fuel Economy testing,
leading from 3-speed to 10-speed transmissions and myriad technologies for improving MpGs,
'they' have never bothered to state a road speed range where a given vehicle gets near its best MpGs.
Whatever the 'city' MpG' cited by the Monroney sticker, it ain't easy to achieve that number.
It's a bit easier on the highway.
I'd prefer they say something like,
'if you want to get at least 2xMpG, keep it under 65MpH on the highway.'