[jaxcam02]

So last month I had the liberty of taking the Collie on a East Coat road trip up to Niagara and NYC from Florida. The week before I drove to Orlando without the air dam and noticed the DIC telling me mpg's were around 21 and my calculated mpg's were 20.3. Before I went for the road trip I decided to put the air dam back on after having it removed from the 1st month I got it. Now keep in mind this was a big trip carrying more people and luggage. I was forced to buy a toolbox for extra storage space as well. Ah hell im going to summarize everything below in a table

----Trip----------airdam-------Passengers------toolbox------approx. weight of luggage----- MPG

Jax to Orl----------NO--------------2---------------No------------------30lbs-------------------20.3

Jax to NY----------YES-------------3---------------YES----------------100+lbs------------------24

Draw your own conclusions from the above information but it is pretty clear that the air dam (maybe the tool box also) accounts for nearly 4 whole MPG's. Both trips were pretty much all highway mileage in very hot conditions and pretty similar humidity. Jax to NY did have a very mountainous terrain compared to FL and with that comes much higher altitudes and lower amounts of oxygen for combustion but still I was able to increase MPG's incredibly with the air dam on.

 

[fondupot]

There's a lot more factors here that could come into play on that long of a drive.

Quality of gasoline
Temperatures
Use of A/C
Wind
etc

These all could account for the difference in 4 mpg's. Even in lab testing scenarios, the Air dam might only increase mpg by 1-2, with all other variables being identical.

The only way to accurately test the air dam's effectiveness would be in a controlled environment (like GM's test lab). Real world situations have too many outside variables.

 

[mnfeo2]

Thanks for the info!

 

[boombots]

I noticed little no difference. Here is motor trends tests... So small that it is negligible.

http://www.motortrend.com/cars/chev...hevrolet-colorado-z71-diesel-review-update-5/

Granted that is diesel but still.

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[jaxcam02]

There's a lot more factors here that could come into play on that long of a drive.

Quality of gasoline
Temperatures
Use of A/C
Wind
etc

These all could account for the difference in 4 mpg's. Even in lab testing scenarios, the Air dam might only increase mpg by 1-2, with all other variables being identical.

The only way to accurately test the air dam's effectiveness would be in a controlled environment (like GM's test lab). Real world situations have too many outside variables.

Let me address those:
-Quality of gas is of course going to be different in locations so that is not a controlled variable at all, although I always use 87
-A/C: I use the ac on full blast everywhere I go. Controlled variable
-Temp: Temps were almost exclusively in the 90's
-Wind: Another uncontrollable variable

Of course there are many variables that are uncontrollable but being at a much higher altitude than florida with limited Oxygen.
My overall weight was higher by at least 300lbs.
Tire pressures were continuously the same.

The only differences in aerodynamics were the air dam and the tool box. Of Course I will have to drive the same route to Orlando again but I have done that route 20 times in the truck and it has been continuous at 19-20 MPGs regardless of temperature, gasoline, weather, etc. without the air dam on the truck

Im a science teacher so I know there are too many variables I cannot quatify but, I think there is enough evidence to conclude that the air dam saved me at least $40 on a 3000 mile trip. lol

 

[JW]

Interesting... a much greater difference than I would have expected to see.

 

[DargelJohn]

Thanks for the analysis. Think I'll leave my air dam on.

 

[fondupot]

Let me address those:
-Quality of gas is of course going to be different in locations so that is not a controlled variable at all, although I always use 87
-A/C: I use the ac on full blast everywhere I go. Controlled variable
-Temp: Temps were almost exclusively in the 90's
-Wind: Another uncontrollable variable

Of course there are many variables that are uncontrollable but being at a much higher altitude than florida with limited Oxygen.
My overall weight was higher by at least 300lbs.
Tire pressures were continuously the same.

The only differences in aerodynamics were the air dam and the tool box. Of Course I will have to drive the same route to Orlando again but I have done that route 20 times in the truck and it has been continuous at 19-20 MPGs regardless of temperature, gasoline, weather, etc. without the air dam on the truck

Im a science teacher so I know there are too many variables I cannot quatify but, I think there is enough evidence to conclude that the air dam saved me at least $40 on a 3000 mile trip. lol

Think what you like, but that $40 is likely in bell curve. Need more data points to have a meaningful analysis. But of course, if it makes you feel better...keep the air dam on. :wink2:

 

[wildwest450]

Another variable is the
Does
Inaccurate
Calculations

Although tri-fecta is to blame for some, mine just read 27.9 mpg at empty, actual calculated was 23.8. Math, how does it work?

 

[jaxcam02]

I've manually recorded every fill up. The Colorado dic always adds 2 mpgs vs calculated. In other words it would always tell me in getting 20 mpg in city but my calculated is 18 mpg. I've recorded every fill up on my all my machines since 2007. When something makes a difference I know about it, maybe not with 100% accuracy but I know its there.

Looking at the graph below you can obviously see my city fill ups and highway fill ups, it has been pretty consistent during the entire life of not having the air dam on.

I also added all my vehicles MPGs for fun in the second graph, BTW before you say anything, I missed a few recordings with my GZ250. No that bike did not get 130 mpg. lol

 

[Payload]

OP, your intentions are sincere but your trip data is not science.
Does anyone challenge corporate GM's motivation to pursue the highest MPG possible within the laws of physics...perhaps even at the expense of a lugging and annoying tranny?
There is no question GM engineering spent considerable resources studying the effects not just of the fugly air dam, which challenges the over all design ethos of the Twins, but also for another example, the automatic radiator louvers. Engineering goals to maximize fuel economy are crucial to satisfying government requirements let alone attempting to appeal to potential consumers' sense of economics. You can't deny MPG ratings are a major buyer consideration even in the utilitarian truck sector.
GM traded off design esthetics for fuel efficiency.
If you want a vehicle that is a product of extensive research in a lab controlled environment leave the damn air dam on.
If design and appearance is your primary interest feel free to remove it.
If off-roading and clearance issues are your bag...go ahead and castrate it.
It is all about owner privilege.
And there is nothing wrong with that.

 

[jaxcam02]

OP, your intentions are sincere but your trip data is not science.
Does anyone challenge corporate GM motivation to pursue the highest MPG possible within the laws of physics...perhaps even at the expense of a lugging and annoying tranny?
There is no question GM engineering spent considerable resources studying the effects not just of the fugly air dam, which challenges the over all design ethos of the Twins, but also for another example, the automatic radiator louvers. Engineering goals to maximize fuel economy are crucial to satisfying government requirements let alone attempting to appeal to potential consumers' sense of economics. You can't deny MPG ratings are a major buyer consideration even in the utilitarian truck sector.
GM traded off design esthetics for fuel efficiency.
If you want a vehicle that is a product of extensive research in a lab controlled environment leave the damn air dam on.
If design and appearance is your primary interest feel free to remove it.
If off-roading and clearance issues are your bag...go ahead and castrate it.
It is all about owner privilege.
And there is nothing wrong with that.

Where have I said its exact science? I have not only once but numerous times stated variables that are beyond control. I have stated to take the information I have provided for face value. All I have presented here is an examination, in my case, of the differences with the thing on or off.
I am not disagreeing that the thing makes the truck look terrible.
No where did I say GM didn't do their research (I would hope they did)
I think your taking things I have said out of context and made a mountain out of a mole hill. If you can dispute anything I have said or presented as not being true (in my case) then by all means dispute it. But since I have not presented this as a peer reviewed scientific article but more of an informal informational approach just take it for what it is, just another guys experience to try to help others make the best monetary decision that they can.
For not being that difficult to remove and install it may be a preference of some to remove it for city driving and reinstall it for long road trips to save gas and money.

 

[Payload]

Please take a deep breath, I said your "intentions are sincere". I said it was not science. I did not use the word "exact". I didn't imply you said it was science.
Sorry, but participation in a forum requires a bit of skin.
Didn't mean to ruffle your feathers as I do recognize your post was meant to be helpful.
All in the spirit of dialogue and meaningful exchange of information.
Chill.

 

[White016]

So last month I had the liberty of taking the Collie on a East Coat road trip up to Niagara and NYC from Florida. The week before I drove to Orlando without the air dam and noticed the DIC telling me mpg's were around 21 and my calculated mpg's were 20.3. Before I went for the road trip I decided to put the air dam back on after having it removed from the 1st month I got it. Now keep in mind this was a big trip carrying more people and luggage. I was forced to buy a toolbox for extra storage space as well. Ah hell im going to summarize everything below in a table

----Trip----------airdam-------Passengers------toolbox------approx. weight of luggage----- MPG

Jax to Orl----------NO--------------2---------------No------------------30lbs-------------------20.3

Jax to NY----------YES-------------3---------------YES----------------100+lbs------------------24

Draw your own conclusions from the above information but it is pretty clear that the air dam (maybe the tool box also) accounts for nearly 4 whole MPG's. Both trips were pretty much all highway mileage in very hot conditions and pretty similar humidity. Jax to NY did have a very mountainous terrain compared to FL and with that comes much higher altitudes and lower amounts of oxygen for combustion but still I was able to increase MPG's incredibly with the air dam on.

Interesting, maybe your truck was lower because of the extra weight? That might help? Maybe the tool box changed the aerodynamics? Maybe you had a tailwind most of the trip? Or headwind on the other? Or both. 4 MPG is A LOT! IMO the wind would make the biggest difference at highway speed.

 

[jaxcam02]

Please take a deep breath, I said your "intentions are sincere". I said it was not science. I did not use the word "exact". I didn't imply you said it was science.
Sorry, but participation in a forum requires a bit of skin.
Didn't mean to ruffle your feathers as I do recognize your post was meant to be helpful.
All in the spirit of dialogue and meaningful exchange of information.
Chill.

It isn't a big deal man. In all honesty I'm trying to get out of my trolling ways and it's harder than I thought to not be a dick online sometimes. I just hate when someone puts words or my mouth or implies it. Especially in an automotive forum because it's one place I can go and not deal with idiocy. Are you at work right now?

 

[DargelJohn]

Where have I said its exact science? I have not only once but numerous times stated variables that are beyond control. I have stated to take the information I have provided for face value. All I have presented here is an examination, in my case, of the differences with the thing on or off.
I am not disagreeing that the thing makes the truck look terrible.
No where did I say GM didn't do their research (I would hope they did)
I think your taking things I have said out of context and made a mountain out of a mole hill. If you can dispute anything I have said or presented as not being true (in my case) then by all means dispute it. But since I have not presented this as a peer reviewed scientific article but more of an informal informational approach just take it for what it is, just another guys experience to try to help others make the best monetary decision that they can.
For not being that difficult to remove and install it may be a preference of some to remove it for city driving and reinstall it for long road trips to save gas and money.

OP, Your comparison makes sense to me. Even though the DIC may not be accurate, you used those values for your Dam off vs Dam on comparison. Apple to Apple.

 

[GH1618]

jax, I'm on your side here. There is no need to analyze this to death, just enough to get a useful result. If you think you're in the ballpark, that's useful.

 

[BobsCreek]

Interesting perspective. I have one section of about 35 miles that I use as a mpg check, it has hills, curves and high and low speed areas... Put bedrack and rtt on yesterday, the rtt is higher than the cab... Upped my mpg on that stretch by 2.2 mpg.. yeah.. I'm not buying it lol

 

[Suns_PSD]

First I want to say I don't think anything looks bad about the air dam, and I'm going to leave mine on my lifted truck.

But you should know the higher altitude actually gets notably better fuel economy due to the less wind resistance, that is common.

It's not like your fuel injected engine runs really rich at altitude like a carburetor would.

Tell you something else that most people don't know, cold intake air while good for horsepower, actually reduces fuel economy. You get a lower heat of vaporation with hot air and this improves fuel economy.

 

[jso902]

Interesting... Thank you for taking the time to do this experiment.
I appreciate the observational study in light of those that are quick to critique.
As for looks, there's already several posts about how good /ugly it looks.

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