Fuel efficiency drop in newer models ?

[viven44]

That's been the case longer than you think. And most electronics need to be coded anyways. Idk that I've ever used dorman for any module lol.

If you can code a 2024 GM module more power to you. Most people need to go to the dealership.

Look at this one guy. His Yukon has a seemingly mundane problem P0304... apparently a GMC corp specialist has been summoned now.... complexity is at a point where even dealers won't be able to fix these things... bottom of my heart I hope I'm wrong about all of this because it would suck if all these vehicles are simply scrapped as cost of repairs would exceed their value quickly.

Cylinder 4 miss-fire P0304

Bought a 2025 yukon denali and have had it in shop multiple times. First intake manifold gasket then a lifter failure. Am telling them to replace coil and plug because they can't seem to fix the cylinder 4 from missfiring. What else would cause this? Computer, loose wire?

www.tahoeyukonforum.com

Topology map on our 2024. I see many things that make my head spin.

 

[DuraYuk]

If you can code a 2024 GM module more power to you. Most people need to go to the dealership.

Look at this one guy. His Yukon has a seemingly mundane problem P0304... apparently a GMC corp specialist has been summoned now.... complexity is at a point where even dealers won't be able to fix these things... bottom of my heart I hope I'm wrong about all of this because it would suck if all these vehicles are simply scrapped as cost of repairs would exceed their value quickly.

Cylinder 4 miss-fire P0304

Bought a 2025 yukon denali and have had it in shop multiple times. First intake manifold gasket then a lifter failure. Am telling them to replace coil and plug because they can't seem to fix the cylinder 4 from missfiring. What else would cause this? Computer, loose wire?

www.tahoeyukonforum.com

Topology map on our 2024. I see many things that make my head spin.
View attachment 457275

Gm has had a mdi box for a long time now. The days of the tech 2 have been over. And there are aftermarket solutions to help the DiY person. With that said idk why you think a dealer won't be able to fix these. Honestly modern diagnostics have come a long way and I love a good modern wiring diagram on a computer over a black and white printed one buried in a stained book.

I love the modern stuff. Its not scary at all.

 

[viven44]

Hey this guy thinks alike.. he drives an early 2000s buick lol

He also talks about the 'conspiracy'... Companies care about making money. They do care about reputation, but they also know people have no better choice these days. Ford / GM / Stellantis are all under the same pressure to cut costs. There is significant competition and everyone has to use all means necessary to cut costs (off shore manufacturing being one of the tricks in this day and age).

 

[rlhmarines]

Fuel economy on these bricks starts to rapidly diminish over 65 MPH. The problem is when people are pushing these bricks at 75-80 MPH, you cannot expect much, this is not how the EPA fuel economy is tested.

Additionally anyone that has a 6.2l is likely using the right pedal a lot to get around slower traffic, just bring up the Fuel Economy display and keep it on the dash, watch what the center portion is showing, you will see what happens on inclines or when the right pedal is used. If the vertical bar drops to around 25% on the fuel economy, you are likely into 80%+ engine loading.

Here a shot of a recent trip I took and I was not trying to be thrifty, I had to meet a deadline. I have done better, but it depends on a lot of factors.

View attachment 457257

I like to keep a similar screen up in the new Tahoe but it doesn’t have the average speed displayed like in yours anymore. I will continue playing around with the display options but I don’t believe it’s available anymore in the refreshed SUV’s.

I told my wife when she was driving on a leg of our trip to keep it below 82 mph to see what kind of mpg we could get on our 6 hr drive. I also believe people are just driving faster without fully knowing the consequences to their fuel economy especially above a certain rpm or mph in these much taller versions that we’re driving now. Our ‘25 Tahoe towers over my ‘01 Tahoe especially the hood area, I almost need a step ladder to reach the dip stick so as to not touch the fender on the new one.

Rpm and how smooth you apply the gas and brakes makes a huge impact on your mileage plus if you live in mountainous terrain or have a good amount of rolling hills you can expect lower than normal fuel economy but your driving style is the biggest factor in my opinion from decades of driving experience.

 

[jfoj]

The Fuel Economy Display is very helpful if and when you start to pay attention and learn how it functions.

You can easily see when you are coasting, on light throttle, pulling grades and so forth and how it impacts your fuel economy.

While not a 100% correlation, I have figured out when the center bar graph drops to around 25% or lower, if the transmission has not downshifted to the point the engine RPM is over 2000 RPM, this is where you start loading the hell out of the engine and using all the Torque. At or below the 25% indication is where you start loading the engine to 80-100% if the engine RPM is under 2000 RPM!!!! Watch this bar graph carefully next time you take a trip and you will soon start to understand where your fuel is going.

 

[Scarey]

I’m wondering if there are any ill effects of driving in tow mode. You give up gas economy but in are in the tourque rang more solidly. You obviously are giving up mpg but it just feels it in a bette spot, quicker response to power. Not lugging as much. Any thoughts?

 

[jfoj]

I have not played with the Tow Mode much yet. As a side not, it has been confirmed that even in Sport and Tow mode, DFM is still active, maybe not as active, but still active.

Typically Tow mode will delay upshifts and may even keep the transmission from shifting into 10th gear?? I also assume Tow Mode may downshift earlier, but again, this is an assumption at this point in time. I do believe Tow Mode also opens the Active Grille Shutters, I played with it on one drive for a short while looking at the the engine and oil temps and I believe the Active Grille Shutters are open, but I would need to put a camera in to watch the shutters or see if I can monitor the shutter behavior with a scan tool. I expect the TCM changes and opening the Active Grille Shutters will impact fuel Economy in a negative way, but by how much, I have no idea.

I may try to pull some data to monitor Tow Mode, but I just have a lot on my schedule at the moment.