Bad mpg?

[Antonm]

Physics is kinda *****, and it says to move an "X" amount of mass at a given velocity, it takes a "Y" amount of energy to do so.

Vehicles have gotten heavier thanks to all the mandated safety stuff , and engine efficiency (the only thing that could possibility give better fuel milage) is being help back by the mandated emissions control equipment.

Just as an example, according to google, the curb weight of a base 2001 Tahoe was 4828 lbs, the curb weight of a base 2024 Tahoe is 5611 lbs.
Interesting side note for perspective, the massive 1972 Suburban (in 2WD) was 5200 lbs curb weight, so a 2024 base Tahoe (also 2WD) is 400 pounds heavier than a 1972 Suburban.

Not a big surprise that fuel milage isn't going up, and in some cases actually going down.
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[jerry455]

My 2021 6.2 Suburban High Country 4wd is 5,360 lbs. I weighed it last time I went to the scrap yard. Currently, around town and 7* degrees this morning, I am getting 12 mpg. I have been remote starting it more lately for my wife. I can get 18-20 on the highway.

 

[Marky Dissod]

GMT K2xx & T1xx have more drag area than GMT900.
Unless you're driving basjoos' AeroCivic, MpG @ 80MpH is always worse than MpG @ 65MpH.

 

[swathdiver]

Just picked up a 2024 Yukon SLT 5.3L RWD and driving back from Florida to North Carolina with only a single stop I'm getting 17.5mpg.

Coming out of Florida you are going up all the time with few hills to drop down on and coast. The engine is almost constantly under a load and climbing in elevation.

The motor just needs to get broken in and she'll loosen up and deliver better mpgs.