MPG difference between 3.08 and 3.42 ratios

[Tiredmechanic23]

I can pull 25mpg highway out of my 2016 with the 3.08 ratio but im curious what people are getting with the 3.42s. I tow from time to time but I also would like the little extra get up and go. 8 months out of the year my town is flooded with traffic heading to the beaches etc and that extra umph would be great to get though traffic with all the lights we have and get to my side routes to avoid traffic. I travel enough long distance though that mileage does matter to me to a degree.

 

[swathdiver]

I can pull 25mpg highway out of my 2016 with the 3.08 ratio but im curious what people are getting with the 3.42s. I tow from time to time but I also would like the little extra get up and go. 8 months out of the year my town is flooded with traffic heading to the beaches etc and that extra umph would be great to get though traffic with all the lights we have and get to my side routes to avoid traffic. I travel enough long distance though that mileage does matter to me to a degree.

I'll bump this and hope some guys with direct experience chime in. I have seen on the pages of this forum fellas reporting nearly the same, 23 MPG with Yukon XL Denalis.

 

[BigtimeBama]

I'll bump this and hope some guys with direct experience chime in. I have seen on the pages of this forum fellas reporting nearly the same, 23 MPG with Yukon XL Denalis.

I get 24 hwy and about 18 around town in a 2015 Suburban with the 3:42

 

[swathdiver]

I get 24 hwy and about 18 around town in a 2015 Suburban with the 3:42

That's great. The mileage these trucks get has piqued the interest of my father. You see he drives a little Kia Soul that averages 24 mpg on the highway and barely has room for all of my mother's luggage for when they travel. They are both still healthy enough in their 70s to climb into my truck so now owning one of their own might come to fruition.

 

[Tiredmechanic23]

That's great. The mileage these trucks get has piqued the interest of my father. You see he drives a little Kia Soul that averages 24 mpg on the highway and barely has room for all of my mother's luggage for when they travel. They are both still healthy enough in their 70s to climb into my truck so now owning one of their own might come to fruition.

That is all those little Kia Souls get? wow im shocked. With such low mileage plus they are known to fall apart and devalue super quick they are almost not worth the metal they are made with.

These SUVs do great for mileage for their size. I have the AFM off with my tune and I imagine with it on plus the tune I could get better than 25 by a couple MPG. But I have the power to tow when I need to for what towing I do plus plenty of room for my 4 kids and all their junk for beach trips etc..

I know they are pricey but if they can afford one or a good used one that was properly serviced they would love it I am sure.

 

[K2 Kaiju]

Im about 20-21 on hwy, but I did trim the chin, add the esky mirrors, and leveled it a bit; maybe the burb is thirstier, although I generally drive around 85...

 

[Christoph]

I get 24 hwy and about 18 around town in a 2015 Suburban with the 3:42

I get 22mpg with my 2015 witht the 3.42's....but it's also a 4x4. Seems like anything after 75mph and it uses more fuel at a higher rate.

 

[Tiredmechanic23]

seems like a small enough difference I may do the swap then. I am only a 2x4 so that should help a touch.

 

[dsh1106]

I have a 2017 Yukon with 308s and a 2017 Tahoe with 342s other than than both are the same. (except trim levels)

The Yukon averages 14 in town and 19 open road, the Tahoe averages 17 in town and 22 open road.

Tahoe has dropped a bit since I bought the Diablo tuner, I'm not sure if its the tune or my modified driving habits.

Hope this helps.
Scott

 

[Bob2C]

I get 15 around town and 24 on highway on my 18 Tahoe 5.3 4x4 3.42 rear AFM off running Diablew 91/93 tune. Transmission and differentials filled with AMSOIL Signature. Don’t know if that makes a difference. Very happy


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[swathdiver]

I get 15 around town and 24 on highway on my 18 Tahoe 5.3 4x4 3.42 rear AFM off running Diablew 91/93 tune. Transmission and differentials filled with AMSOIL Signature. Don’t know if that makes a difference. Very happy


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I reckon those Amsoil products are worth at least 1 mpg Robert, great stuff!

 

[Bob2C]

I reckon those Amsoil products are worth at least 1 mpg Robert, great stuff!

I think so. I am also running AMSOIL xl in the engine for the first time. I think I would be waisting the signature changing it out at 6k mike intervals. I still run the ac Delco PF63e. I’m happy


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[exp500]

Alot of discussion on gears no matter which section of forums you are in..... Mileage, performance, towing, Offroad. Simple explanation is 308/342/373/410/455 - each step is about as close to 10 percent as you can get- So any changes one step will be minimal, about the same as 2 different drivers. Takes a 2 step jump to be significant. So in the end it comes down to how you drive. Over 80 need 373 or less(engine RPM). Always remember, the faster you spin driveshaft, the more relible the driveline is (less stressed).

 

[59yukon01]

Have a 2016 Yukon with the 3.42. Last trip from KY to FL and back I averaged 20-21 on the hwy, but that was at pretty much a constant 80 MPH.

 

[stallion_412]

2015 Yukon 4x4 5.3l engine w/ 3.42 rear end. Average 23-24mpg at 75mph.

What really surprised me is how much better it is than my pickup which has the same powertrain. My pickup only gets ~19-21mpg at 75mph, depending on a lot of conditions.

 

[BG1988]

I reckon those Amsoil products are worth at least 1 mpg Robert, great stuff!

tell gm so it can come with it from the factory

 

[BMPNUGLS]

I have a 2016 Yukon XL Denali (4wd) with 6.2L and 3:42’s. Range AFM Disabler always plugged in. It’s got 95K miles (regional account manager so lots of windshield time)...on average I get 23/24 Hwy and 15/16 in town. BUT I have also done a couple long trips with cruise set at 65mph and got 28mpg!
I do keep all maintenance up religiously, have a AEM dry flow air filter, clean the MAF sensor & air filter every couple months, and run a personal concoction mix of fuel system cleaners at least once a month with a fill up. Not sure if any of that matters but thought I’d mention it.

I should also add that I always (for the most part) use 93 octane fuel or at least 91....preferably Shell or BP.

To this day I’m still amazed at the mileage I get with the 6.2 and brag about it every opportunity I get! Lol

 

[RST Dana]

View attachment 254795 I have a 2016 Yukon XL Denali (4wd) with 6.2L and 3:42’s. Range AFM Disabler always plugged in. It’s got 95K miles (regional account manager so lots of windshield time)...on average I get 23/24 Hwy and 15/16 in town. BUT I have also done a couple long trips with cruise set at 65mph and got 28mpg!
I do keep all maintenance up religiously, have a AEM dry flow air filter, clean the MAF sensor & air filter every couple months, and run a personal concoction mix of fuel system cleaners at least once a month with a fill up. Not sure if any of that matters but thought I’d mention it.

I should also add that I always (for the most part) use 93 octane fuel or at least 91....preferably Shell or BP.

To this day I’m still amazed at the mileage I get with the 6.2 and brag about it every opportunity I get! Lol

What’s that song?
I can’t drive 65!

me either, that’s why I average 20-23 at 80.

 

[swathdiver]

What’s that song?
I can’t drive 65!

me either, that’s why I average 20-23 at 80.

On the way to Daytona last week mine averaged 16.2 MPG at 78 MPH. 3.42 gears, no VVT, no AFM. AT Tires.

 

[BMPNUGLS]

What’s that song?
I can’t drive 65!

me either, that’s why I average 20-23 at 80.

Ya the drive to one of my accounts is mostly 2 lane country road all the way there...w troopers everywhere along the route...lol. But I’ll still get 22+ running 80+ on I-70 usually