Bad mpg?

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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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.

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

onyx24 said:

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.

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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.

swathdiver said:

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

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How long does this “ loosen up” take? Ours has 17k miles on it now and still gets about that same mileage, sometimes even worse.

I reset the #1 trip odometer (which also has a fuel economy attached) every time I get gas and leave the #2 trip odometer alone/ never reset it. So in theory, I should have short term (each fuel tank) and a long term fuel economy averages, both numbers are pretty similar , and pretty close to the OP number.

I have a 2024 XL 4x4 5.3L with just over 8,000 miles. Florida to Southern Illinois driving 75-85 mph I averaged just over 20 mpg on a round trip. My mileage improved at around 5,000 miles. It loves traveling at a constant speed. Adaptive cruise keeps changing the speed depending on traffic. I changed to the old style cruise setting and my mileage improved. It also doesn’t make my wife car sick with the drastic speed changes.

My best 50 mile mpg was 27 mpg traveling at 45 miles per hour. Not by choice road construction on a different trip. That was 2 hours of my life that I won’t get back. Flat road, no wind, traveling almost bumper to bumper.

I have had an 84, 96, 09, 15, and now a 2024. All purchased new and with the exception of the 2024 they all hit 150,000 before I traded. The 2015 and 2024 had the best mpg by far. Better than I ever expected. The 1984 was good for at best 16 mpg at 65 mph on the interstate. 12 when I towed my boat.

tom3 said:

Wow. That's about what these machines got 20 years ago.

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Yep, all that tech and the mileage actually got worse with the latest Gen (except diesel). Not that you buy one for the mpg's.....

Antonm said:

How long does this “ loosen up” take? Ours has 17k miles on it now and still gets about that same mileage, sometimes even worse.

I reset the #1 trip odometer (which also has a fuel economy attached) every time I get gas and leave the #2 trip odometer alone/ never reset it. So in theory, I should have short term (each fuel tank) and a long term fuel economy averages, both numbers are pretty similar , and pretty close to the OP number.

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Some of this is computer controlled, the rest is mechanical. I had a new GM minivan that got terrible mileage until she hit the magic number of 9,000 miles. After that, she delivered exceptional performance and gas mileage for what it was.

vcode said:

Yep, all that tech and the mileage actually got worse with the latest Gen (except diesel). Not that you buy one for the mpg's.....

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They basically used the same engines as the K2s and these are much larger vehicles and heavier too. I didn't expect them to be more efficient than the K2s.

When a T1 pulls up next to my old 900, their hoods tower over mine and the cab seems to be a few inches higher. They also run larger diameter tires.