Gas Mileage Differences

mfennema · March 16, 2009

I was speaking with a buddy of mine the other day and he drives an 07 Sierra Crew Cab, which is the same as mine. I was tellin him that I get around 17 to 17.5 mpg on average over the entire tank. He was sayin that he only gets about 12.5 to 13 mpg. Anyone have any ideas on why there is such a huge difference? He was sayin that his AFM rarely puts his truck in V4 whereas mine goes into V4 anytime I am not going uphill or pushing on the accelerator.

Can someone run build sheets on these two VIN's? I want to see if there is some glaring difference between my truck and his that we just don't see which is causing this fuel mileage difference.

2GTEK13M071537518 - His

2GTEK133971658538 - Mine

Thanks!

66nova · March 16, 2009

Assuming you are using DIC to tell you this information and assuming that both of you reset the DIC immediately after each fill up then I would have to say it is a combination of Driving styles, driving locations (town, stop and go, highway, what highway speeds, etc) and idle time. Letting the truck idle a little can change the fuel mileage a lot.

My guess is, if his AFM does not kick in much, he is driving with a heavier foot.

With my 6.0 I change my mileage from tank to tank a lot with different driving senarios and mood. People who get pissy behind the wheel tend to get a couple mpg less than people who stay calm.

pchrist · March 16, 2009

Yeah i would be interested too. I get about 11.5 in mine. I have been trying to be more conservative and it isn't helping at all!!!!. was on the highway sat with a fresh tank and only got 15mpg for 70 on the highway with cruise on. Doesn't seem right.

jrrod2004 · March 16, 2009

question for you....what is the mileage on his odometer and yours. I was told that the longer the engine is broken in, the more 'fuel efficient' it gets...

mfennema · March 16, 2009

question for you....what is the mileage on his odometer and yours. I was told that the longer the engine is broken in, the more 'fuel efficient' it gets...

Mine has about 32k and his has about 16k. The only time I noticed my mileage get considerably better was when I added my Extang Revolution cover. That said, he also has a cover on his truck but still doesn't get nearly the mileage that I get.

I believe that our driving styles are pretty similar based on times that I've ridden with him. Only difference may be that I drive a few more hwy miles than he does on a day to day basis, but even when I lived in Chicago and drove through that road construction nightmare every day, I still got 15.5 mpg.

jrrod2004 · March 16, 2009

question for you....what is the mileage on his odometer and yours. I was told that the longer the engine is broken in, the more 'fuel efficient' it gets...

Mine has about 32k and his has about 16k. The only time I noticed my mileage get considerably better was when I added my Extang Revolution cover. That said, he also has a cover on his truck but still doesn't get nearly the mileage that I get.

I believe that our driving styles are pretty similar based on times that I've ridden with him. Only difference may be that I drive a few more hwy miles than he does on a day to day basis, but even when I lived in Chicago and drove through that road construction nightmare every day, I still got 15.5 mpg.

My only guess would be that the difference in mileage ("Age") of the engine is what could be a contributing factor. Most guys tell you that when then engine is brand new (less than 3000 miles), it sucks gas like crazy, as you start piling up the mileage, it gets better and better up to a point - I want to say around 25-40,000 miles. After that, then its all maintenance to keep it up. By the way, what is the rear end gear of his and yours?

mfennema · March 16, 2009

question for you....what is the mileage on his odometer and yours. I was told that the longer the engine is broken in, the more 'fuel efficient' it gets...

Mine has about 32k and his has about 16k. The only time I noticed my mileage get considerably better was when I added my Extang Revolution cover. That said, he also has a cover on his truck but still doesn't get nearly the mileage that I get.

I believe that our driving styles are pretty similar based on times that I've ridden with him. Only difference may be that I drive a few more hwy miles than he does on a day to day basis, but even when I lived in Chicago and drove through that road construction nightmare every day, I still got 15.5 mpg.

My only guess would be that the difference in mileage ("Age") of the engine is what could be a contributing factor. Most guys tell you that when then engine is brand new (less than 3000 miles), it sucks gas like crazy, as you start piling up the mileage, it gets better and better up to a point - I want to say around 25-40,000 miles. After that, then its all maintenance to keep it up. By the way, what is the rear end gear of his and yours?

I am not sure. That is one of the reasons I was wanting to see if I could get the build sheets.

txab · March 16, 2009

Build sheets are available from the dealer. That info can't be posted here. Thanks GM.

pchrist · March 16, 2009

15k on mine and the gas still gets sucked down. Even when i drive conservative!!!

music · March 16, 2009

I've had very good mpg numbers since my truck was brand new (never avg less than 16.5, and often over 19 with mixed/70% hwy using 87 octane). Recently, I decided to fill up with 91 octane, since prices are so low, just to see. It's early in the tank, but so far, mpg seems to have taken a significant hit. I'll watch the rest of the tank and see how it goes. I guess the point is that fuel selection (brand, type) could also make a difference. I only have 5k on the odom...

mfennema · March 16, 2009

Build sheets are available from the dealer. That info can't be posted here. Thanks GM.

Well ain't that a bunch of crap. Thanks for the info!

MikeInCtown · March 16, 2009

Just to last.

Driving styles MAY seem similar, but there is a huge difference in the DIC numbers just by applying just a hair more throttle on my truck. so much so that I have seen a 4mpg or higher instant econ swing. (16-22 in some cases) I can also be driving and showing 20 with alight touch but pop it into cruise and it will show 22.

Gasoline formulations may also change the mileage as they use different additives with each company.

crepitus · March 16, 2009

15k on mine and the gas still gets sucked down. Even when i drive conservative!!!

i am with you on the "sucking down gas". My 08 EX Cab 4x4 5.3 3.73 gears with 4k miles is getting around 13.5 - 15 mpg. 15 is the best I have seen.

DBVille · March 16, 2009

Assuming you are using DIC to tell you this information and assuming that both of you reset the DIC immediately after each fill up then I would have to say it is a combination of Driving styles, driving locations (town, stop and go, highway, what highway speeds, etc) and idle time. Letting the truck idle a little can change the fuel mileage a lot.

My guess is, if his AFM does not kick in much, he is driving with a heavier foot.

With my 6.0 I change my mileage from tank to tank a lot with different driving senarios and mood. People who get pissy behind the wheel tend to get a couple mpg less than people who stay calm.

Just to last.

Driving styles MAY seem similar, but there is a huge difference in the DIC numbers just by applying just a hair more throttle on my truck. so much so that I have seen a 4mpg or higher instant econ swing. (16-22 in some cases) I can also be driving and showing 20 with alight touch but pop it into cruise and it will show 22.

Gasoline formulations may also change the mileage as they use different additives with each company.

Driving style is pretty much it. My wife gets worse gas mileage than I do, and she can't figure out why. Its the little things - lifting a little earlier cresting a hill, or approaching a stop. Every time you touch the brake, think of it as dumping a cup of gas out. You have accelerated and now are throwing it away. Notice that people who get better mileage are driving with fewer brake applications.

Mazer18 · March 16, 2009

I was only getting about 12mpg in my RCLB back in the colder months. Now I'm getting about 14 with the warmer weather though. I remember when I first got my truck though I was getting around 18-19 mixed driving.

Anyway, I just added a DIC recently which has read between 13.9-14.3 for the past month.....you're supposed to reset it after each fill up?

By the way, mfennema you can find out you and your buddies rear axle ratio on the list in the glove box. Rear axle ratio can make quite a difference in MPG as higher ratio's are geared toward economy where lower ratios are better for power.

Here's the codes to the best of my kowledge:

GU5 = 3.23

GU6 = 3.42

GT4 = 3.73

GT5 = 4.10