2014+ Gas Mileage (MPG) Topic

[Tattooo]

Thats great milage ventilator....I forgot to mention I am using 87 octane

[Mark L]

Just logged a quick trip yesterday with my Sierra Denali (6.2L), 91 octane, got my best mileage to date:

 

Edited July 28, 2014 by Mark L

[calgator73]

We have a nice level stretch of road and I decided to mess with tow haul. 55 no tow haul instant fuel econ was 23-24. Same exact route with button on tranny would only go up to 5th (almost 2k rpm) but instant was 26-27. V4 in both instances. What is the optimum rpm for fuel economy with these trucks?

[2happyhicks]

Ive tried all types of fuels 87, 89, 91, 92, and 93..and various combos of all... my lifetime avg is 16.7 and best mpg I can muster over a tank is 17.8... and thats 100% highway.. ive got 5.3 w/3.08s.... how are 6.2s with 3.42s getting better mpg?

[CAtaylor]

Ive tried all types of fuels 87, 89, 91, 92, and 93..and various combos of all... my lifetime avg is 16.7 and best mpg I can muster over a tank is 17.8... and thats 100% highway.. ive got 5.3 w/3.08s.... how are 6.2s with 3.42s getting better mpg?

More than likely because the 3.42 gears raise the rpm and keep the engine from lugging. I am running 4.56 gears and am turing around 2200 rpm at 70 mph. I am getting 17.3 mpgs there where I was only getting 14.5 with the 3.42 gears running around 1600 rpm. Your engine load is simply higher with the 3.08 gears than it would be with the 3.42 gears at that speed. Keep in mind I am running 35" tires and a 6" lift. I am not saying high rpm is a good thing, at some point the mileage will start going back the other way. Try running the truck in 5th on the highway and see what it does. Use tow haul and find the point where it will stay in 5th but still go into 4 cylinder mode and see how it affects the mileage.

[Mark L]

Ive tried all types of fuels 87, 89, 91, 92, and 93..and various combos of all... my lifetime avg is 16.7 and best mpg I can muster over a tank is 17.8... and thats 100% highway.. ive got 5.3 w/3.08s.... how are 6.2s with 3.42s getting better mpg?

 

 

How fast do you drive?

 

I took my Denali to San Diego and back, put about a 1K miles on it and averaged 20.6 MPGs the entire trip.

 

I kept the cruise right around 73-74 mph the entire trip.

 

And this did include spurts of L.A. traffic.

[calgator73]

Ive tried all types of fuels 87, 89, 91, 92, and 93..and various combos of all... my lifetime avg is 16.7 and best mpg I can muster over a tank is 17.8... and thats 100% highway.. ive got 5.3 w/3.08s.... how are 6.2s with 3.42s getting better mpg?

Try sticking with 89 and on the hwy get up to about 75-78. With your gearing that should put you around 1800 rpm. My 3.73s seem to do really well at about 70-72.

[Mike1220]

More than likely because the 3.42 gears raise the rpm and keep the engine from lugging. I am running 4.56 gears and am turing around 2200 rpm at 70 mph. I am getting 17.3 mpgs there where I was only getting 14.5 with the 3.42 gears running around 1600 rpm. Your engine load is simply higher with the 3.08 gears than it would be with the 3.42 gears at that speed. Keep in mind I am running 35" tires and a 6" lift. I am not saying high rpm is a good thing, at some point the mileage will start going back the other way. Try running the truck in 5th on the highway and see what it does. Use tow haul and find the point where it will stay in 5th but still go into 4 cylinder mode and see how it affects the mileage.

17.3 mpg? Dang. You must take it really relaxed when you're driving. To get that with a 6 on 35s

 

 

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[CAtaylor]

17.3 mpg? Dang. You must take it really relaxed when you're driving. To get that with a 6 on 35s

 

 

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The 4.56 gears really helped it out. That is why I was mentioning the rpm and load. At 70 it will hold 4 cylinder mode the majority of the time.

[Mike1220]

The 4.56 gears really helped it out. That is why I was mentioning the rpm and load. At 70 it will hold 4 cylinder mode the majority of the time.

What if you get a 4" on 33s or 34s? Would 4.56 gears be overkill or is there a gear ratio that would be better? Also where would be a good place to get a good set of gears? I may get them installed when I get my lift and tires if my bank account isn't entirely drained haha

 

I currently have the 3.42 gears in mine if it helps.

Edited July 31, 2014 by Mike1220

[CAtaylor]

What if you get a 4" on 33s or 34s? Would 4.56 gears be overkill or is there a gear ratio that would be better? Also where would be a good place to get a good set of gears? I may get them installed when I get my lift and tires if my bank account isn't entirely drained haha

 

I currently have the 3.42 gears in mine if it helps.

I would go 4.10 with that size tire, the 4.56 would probably be a little overkill. Currently there is only one company (East Cost Gear) that will provide parts to swap the gears on the new trucks and no one actually makes a gear set for them yet. You have to convert it to a 2013 rear end. I have a thread on the conversion though and if you have questions just call them up. They are good guys to work with.

[Mike1220]

I would go 4.10 with that size tire, the 4.56 would probably be a little overkill. Currently there is only one company (East Cost Gear) that will provide parts to swap the gears on the new trucks and no one actually makes a gear set for them yet. You have to convert it to a 2013 rear end. I have a thread on the conversion though and if you have questions just call them up. They are good guys to work with.

Thanks man. And switching to 4.10 gears would help the mileage stay up? Or atleast decrease how many MPGs I lose?

[Mad Max]

 

So i set the cruise control at 57MPH from Concord NH to Boston about 75 miles and this is what I got: almost 27MPG!

[CAtaylor]

Thanks man. And switching to 4.10 gears would help the mileage stay up? Or atleast decrease how many MPGs I lose?

No problem and yes they should help. It wont be dramatic but it will help. Also, it is easier on the driveline of the truck and you will regain most if not all of the lost performance from the lift and heavier tires.

[BRuss0426]

Just had the odometer service update done on my truck, and it seems as if my truck is having to relearn its tolerances between V4 & V8 mode. Has anyone else had this experience?