Fuel efficiency drop in newer models ?

[viven44]

Nice. What's the story with the Ford truck? Is that an F250?

It’s a 1986 F350 4x4 4-speed w/460 w/Dana 60 front axle, all factory stock , 1 owner since 89’, 169k miles, came from Oregon. Bought from daughter in TX after dad passed away. I could have drove it back 200 miles but didn’t have a driver.

 

[viven44]

Good thing I don't live in Texas. I'd have a yard full of vehicles!

I live on a 1/4 acre and have about 4 classics, and 2 daily drivers. Wife is mighty pleased

 

[strutaeng]

It’s a 1986 F350 4x4 4-speed w/460 w/Dana 60 front axle, all factory stock , 1 owner since 89’, 169k miles, came from Oregon. Bought from daughter in TX after dad passed away. I could have drove it back 200 miles but didn’t have a driver.

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Very nice! What are your plans for it?

I too have a old vehicle "dealership" at my house LoL

2020 3500 Express passenger van
2013 Chrysler minivan
2006 Suburban 2500 2wd
2004 Suburban 2500 4x4 (project Suburban)
2000 K3500 CCLB SRW (dump-run/weekender work truck)
1999 Silverado 1500

Wife says I have too many old trucks. SMH

 

[viven44]

Nice, you are really in the thick of GMT800... The daily drivers are in my signature, but really until I got the 02' Yukon I alternated between my 84 F350 (2WD) and 1978 Bronco. It is nice to get double digit mpg in the city on the 02' Yukon

I'm tired of big restorations (like my 78 Bronco!), that I why I paid good money for something original and unrestored and in regular use here. This truck really doesn't need anything... Only needs R134a conversion and really minor things here and there ...

 

[vincentc77]

Anyone notice the he has the Z71 package? Tire rolling resistance has to come into play - just not sure how much that would impact since Ive never had the Z71 or similar AT tires on any of my rigs.

 

[JayceeP]

Hi all,

We just bought a 2024 Suburban Z71 with the 5.3 and 10 speed transmission... now before I go further, I am not very concerned about fuel efficiency (otherwise we wouldn't have bought the vehicle) I am simply making observations and expressing some level of disappointment in engineering decisions that haven't benefited everyone...

Compared to the 2018 with the 5.3 and 6 speed transmission we used to have we are noting that real world fuel efficiency

- in the city is slightly better in the newer model (13mpg vs 15mpg)
- on the highway we are noticing a significant drop in fuel efficiency. On our 2018 if we drove it well we averaged 26-27 mpg whereas on the 2024, we are maxing out at about 18 mpg... (when we had the Range AFM dongle plugged in on the 2018 we still averaged about 24-25mpg...)

The low-end torque was also honestly better with the 2018 with the 6-speed transmission.

The official ratings (from fueleconomy.gov) are definitely supportive of our observations that the outgoing models were better in fuel efficiency.

No change in Tow ratings vs the outgoing model

I loved the 6-speed and it was easy to service and maintain (relatively easily dropping pan, change filter, change fluid, monitor via dipstick). The 10-speed's oil pan is right under the exhaust and looks like both the driver and passenger side manifolds have to be undone to even drop the pan.

I don't see any articles or discussion over this. Being in the engineer profession myself, I am not seeing a better "Figure of merit" with the new technology. Hopefully somebody can educate me on what I am missing.

Not to contradict you but I don’t know in what world I’d expect to get 26-27mpg in a V8 Chev Suburban. Maybe very flat, perfectly paved country roads doing 55mph…. But that is in no way a realistic highway number if you’re driving over 70mph.

 

[viven44]

Not to contradict you but I don’t know in what world I’d expect to get 26-27mpg in a V8 Chev Suburban. Maybe very flat, perfectly paved country roads doing 55mph…. But that is in no way a realistic highway number if you’re driving over 70mph.

Unless the estimate shown by the computer was incorrect that's what we saw on the highway. It was 2WD, not sure if that helped. My wife drove it most of the time and she is a very conservative driver. I can guarantee that I have never seen below 24mpg in the trips I took.... but then again, I never confirmed that with actual fuel up data.

 

[viven44]

We have started logging fuel economy pen/paper on the 2024 like I do on my trucks.

I just filled up gas

Sadly, the first fuel up only net us 12.2mpg over 272 miles of which ~30 miles were highway.. the 02 Yukon does about the same or better, actually I get better highway fuel economy on my 84 with a 460 big block / 3-speed transmission than this 2024 does in the city… seem like a fair comparison on things over 40 years apart? lol

2024 suburban first log (wife to maintain this lets see)

2002 Yukon log (I keep this log)

 

[jfoj]

My 2005 Yukon Denali XL AWD 6.0l with 275,000 miles will get about 14-15 on the highway, but I am not very nice to it, usually 65-75 MPH. Over 65 the MPG starts to crater.

If I slow down and drive 55-60 MPH it may get high 15 MPG or close to 16 MPG but that's tops.

If I hang an enclosed trailer on the back, mileage drops to close to 10 MPG regardless of speed!

My 2024 has been able to get close to 25 MPG on red roads, fairly flat 45-55 MPH without stops or traffic. But hitting the highway hard dealing with and working my way around traffic about 18-19 MPG, sometimes a bit higher depending on traffic. The right foot really hurts the economy, but I can sure get around traffic!

 

[B-train]

One way they meet ever stricter standards is to change the stoichiometric table the engine refers to for Lambda or AFR. I found my 2008 with a 6.2L has a slightly more generous table than the identical 2014 Denali with a 6.2L (granted its a flex fuel motor, so that may be a contibutor). It's only fractions of a percent, but the numbers get lower as the rpm table increases. Lower numbers = more fuel used (keep cats hot - maybe different elements in them?). I want to find a 2000 era truck to pull the file from for reference to add to my findings, but haven't searched aggressively yet.

I did a test on my 2008 and made the AFR 14.6 all the way up to 33% throttle (it drops off steadily past idle throughout the entire rpm range). The first trip out it sounded different through the exhaust note - it reminded me of my 2000 silverado with a 5.3L. So far, fuel economy is slightly better with the changes which follows a slight leaning of the ratio - running regular 87 at the moment.

I'm still in exploratory mode, but I think this is one of the many tricks used to meet the stupid EPA tailpipe emissions. BURN MORE FUEL to have "cleaner" exhaust! No different than what they do for diesels.......Idiots......

Hence the absurd amount of soot on newer gasoline engine tailpipes. Especially the direct injected motors. Watch the dude driving the Kia next to you when he floors it to get ahead in traffic. LOL