Gas Mileage Question

[The Saint]

This is not about The SSR rather it is about Chevy trucks and the difference in mileage. A good friend of mine was looking for a new Truck and I have told him that my 2003 Chev Ext, Cab 4x4 with the 4.8 litre engine gets about 24 MPG on the HWY, now this is Canadian which would translate to approx 20 MPG US, I think this information pursuaded him to go and buy a new Chev 2007 Silverado with all the bells & whistles, It is also a 4X4, he has only about 1000 miles on it but on the HWY only got about 17 MPG Canadian or Roughly 14 USA, any way I am feeling a bit bad for him and am wondering why the difference. Here is what I know about the Trucks they both seem to rev the same at similar speeds.

MINE 2003 - HIS 2007

4.8 Litre - 4.8 Litre
4 speed Auto -4 speed auto
EXT Cab - EXt Cab
100,000 Miles -1,000 miles
4x4 on the floor shift manual - 4x4 electronic
Towing package - Towing Package
No traction Control - Yes traction Control
NO Posi Trac -Yes some sort of limited slip Posi
Not sure but Maybe 3.73 - 3.42 rear end
Tires 16 inch - Not sure but larger Than 16 I think 17

I am wondering will his mileage increase this much after the break in ( I hope so ) or could there be something about the auto 4x4 as that seems to me to be the only difference. My 2003 did not seem to need a break in to get better milage and I am the faster driver so I don't believe it would be that. I normally drive about 75MPH and my friend about 65mph anyway just thought i would ask.

The Saint

[WOW_FCTR]

What is the Manufacturer's MPG rating for each? (just to start the comparison).


[I can look it up if you give me the exact models]

[The Saint]

The 2007 is 25 MPG canadian
The 2003 I believe was 24MPG

My friend also told me that GM rates the 2007 model with the same drive train at 27 MPG if it has the 3.73 rear end as his has the 3.42 I would think it would be better on fuel but it is rated Lower than the 3.73 at 25 MPG hope this helps, my 2003 may have the 3.73 but i am not sure

The Saint

Just thought of something else, mine has a tonue cover and his does not have anything no cover or cap. I would hate to tell him that is the difference without being sure,

[WOW_FCTR]

Originally Posted by The Saint

The 2007 is 25 MPG canadian
The 2003 I believe was 24MPG

My friend also told me that GM rates the 2007 model with the same drive train at 27 MPG if it has the 3.73 rear end as his has the 3.42 I would think it would be better on fuel but it is rated Lower than the 3.73 at 25 MPG hope this helps, my 2003 may have the 3.73 but i am not sure

The Saint

Just thought of something else, mine has a tonue cover and his does not have anything no cover or cap. I would hate to tell him that is the difference without being sure,

Well you are quoting highway miles only and not in town mileage. I would expect somthing like 17/25MPG.

The big difference could be if he's just driving a couple of blocks waiting in a drive thru and driving home, while you commute 30 miles on a highway.


I can easily get <12 MPG with my SSR, just by driving in town hitting the gas. And I can get 20MPG by hitting the highway.

[The Saint]

I was comparing apples to apples. I would think both these trucks should get about the same mileage was just wondering if the difference could be the rear end or the traction control, or something like that. Should a 3.42 rear end get better mileage than a 3.73, seems not as Chevy lists the 3.73 at 27 MPG HWY and the 3.42 at 25 MPG Hwy.

[TLC5 in CT]

Originally Posted by The Saint

I was comparing apples to apples. I would think both these trucks should get about the same mileage was just wondering if the difference could be the rear end or the traction control, or something like that. Should a 3.42 rear end get better mileage than a 3.73, seems not as Chevy lists the 3.73 at 27 MPG HWY and the 3.42 at 25 MPG Hwy.

Apples to apples, the 3:42 should result in better milege than the 3:73.

[olaferickson]

I get about 11 mpg on average between hwy and city, am I doing something wrong? LOL.

[Paul Simpson]

The Saint

Just thought of something else, mine has a tonue cover and his does not have anything no cover or cap. I would hate to tell him that is the difference without being sure,[/quote]

I think you may have hit upon something important in this discussion here. If you read the propaganda published by any toneau, or bed cover seller, you will find that they all claim to increase fuel mileage. This is due to the wind flow over the cab and against the tailgate. This is also the reason for the proliferation of skeletal aftermarket tailgates at one time.
Another thing that continues to haunt me on this subject, is the diff ratio. On this board, I have seen more than one Fanatic proclaim better fuel mileage after changing gears to 4.10s. I believe the same could hold true for your friend, but perhaps a change to 3.73s.
Those two points should be the answer to your mystery.......Paul

[ssr71]

Originally Posted by The Saint

I was comparing apples to apples. I would think both these trucks should get about the same mileage was just wondering if the difference could be the rear end or the traction control, or something like that. Should a 3.42 rear end get better mileage than a 3.73, seems not as Chevy lists the 3.73 at 27 MPG HWY and the 3.42 at 25 MPG Hwy.

I think the 3.42 gears actually hurt as it forces the driver to apply more gas to get the same "go power" feeling. My '99 Silverado has the 3.42 gears and it's not the greatest on mileage. My SSR does way better on the highway! Seems that 3.73 gives the 4.8 and 5.3 engines that sweet spot as far as MPG. Now, because I want to go up to 20" wheels and help out with towing duties, I plan to upgrade mine to 4.10 gears.

Now, your friend's truck is still "new", so give it a bit of time too. These engines definitely start to get better MPG as they break in.

[ssr71]

Originally Posted by olaferickson

I get about 11 mpg on average between hwy and city, am I doing something wrong? LOL.

If your avatar picture is any indication, it's your right foot's fault.

[ssr71]

Originally Posted by Paul Simpson

The Saint

Just thought of something else, mine has a tonue cover and his does not have anything no cover or cap. I would hate to tell him that is the difference without being sure,

I think you may have hit upon something important in this discussion here. If you read the propaganda published by any toneau, or bed cover seller, you will find that they all claim to increase fuel mileage. This is due to the wind flow over the cab and against the tailgate. This is also the reason for the proliferation of skeletal aftermarket tailgates at one time.
Another thing that continues to haunt me on this subject, is the diff ratio. On this board, I have seen more than one Fanatic proclaim better fuel mileage after changing gears to 4.10s. I believe the same could hold true for your friend, but perhaps a change to 3.73s.
Those two points should be the answer to your mystery.......Paul[/quote]

You can pretty much discount the bed cover. I have one and didn't see any change. Mythbusters had an episode where they ran tests on 3 of the most common gadgets/methods of trying to get better MPG on pickups. The mesh tailgate actually performed best, but running with gate down made it worse. However, these differences were in fractions of an MPG, so it's not like you can jump from 17mpg to 21mpg simply by putting a bed cover on.

[The Saint]

Well thanks again, all for your input, I suspect it has something to do with the 3.42. I talked to my friend again and he also told me he had it on cruise control and on every hill the truck would kick down and rev up to maintain speed up the hills, on the same strech of highway my truck will go up most all of the same hills without doing this so I suspect my truck has different ratio rear end and although it may be higher Ie. 3.73 it does in fact suit the vehicle better and may give it better gas mileage vs. the 3.42 which you would think at least at first glance would be better on gas but Chevy does rate the 3.73 models higher in gas mileage than the 3.42. I will stop now as i am confusing myself .

The Saint

[DOOPHUS]

Originally Posted by The Saint

Well thanks again, all for your input, I suspect it has something to do with the 3.42. I talked to my friend again and he also told me he had it on cruise control and on every hill the truck would kick down and rev up to maintain speed up the hills, on the same strech of highway my truck will go up most all of the same hills without doing this so I suspect my truck has different ratio rear end and although it may be higher Ie. 3.73 it does in fact suit the vehicle better and may give it better gas mileage vs. the 3.42 which you would think at least at first glance would be better on gas but Chevy does rate the 3.73 models higher in gas mileage than the 3.42. I will stop now as i am confusing myself .

The Saint

Here's another point to help with your "confusion", The Saint.

Similar to what your friend describes, cruising at 65 MPH with the Cruise Control on, my '87 Chevy Silverado 4X4 with the famous GM 350 V8 would always downshift on a long incline that I traveled frequently, sometimes even twice. After a complete dual exhaust system installation, NO MORE DOWNSHIFTS and my gas mileage jumped from about 15 to 18 MPG.

As promised . . . another point to add to the confusion.

Curt

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