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MPG Head Scratching

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Old Jun 8, 2011 | 10:51 AM
  #1  
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Question MPG Head Scratching

I have a question to ask. Yesterday, I made a 150 mi rt drive that I have made three other times since I have owned the truck, as recently as last week. I have consistently averaged 18 to 19 mpg. Same weather conditions as previous trips I averaged 16 to 17mpg. The only difference, my factory installed bed cover was rolled up.

Has anyone else ever observed this or am I chasing moonbeams?
 
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Old Jun 8, 2011 | 10:56 AM
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When I put the bed cover on my new truck I thought the mpg went down. Winter gas (gas truck)?
I have been watching the mpg lately and now it doesn't seem to make any difference.
I'd also like to know if a bed cover can alter mpg.
 
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Old Jun 8, 2011 | 11:14 AM
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Originally Posted by Ricohman
When I put the bed cover on my new truck I thought the mpg went down. Winter gas (gas truck)?
I have been watching the mpg lately and now it doesn't seem to make any difference.
I'd also like to know if a bed cover can alter mpg.
It's been proven that a bed cover does nothing for MPG. There is a high pressure bubble that forms in the bed when there is no cover that acts as if there is a cover.
 
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Old Jun 8, 2011 | 11:32 AM
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Originally Posted by Ricohman
When I put the bed cover on my new truck I thought the mpg went down. Winter gas (gas truck)?
I have been watching the mpg lately and now it doesn't seem to make any difference.
I'd also like to know if a bed cover can alter mpg.
It's been proven that the air "bubble" that exists behind the cab actually smooths out the airflow over the truck. Lowering the tailgate or using a flow-through tailgate prevents the bubble from forming and actually increases drag on the truck. Removing the tailgate all together has some improvement in mileage due to the decrease in weight but even that benefit is lost due to the increased drag of no bubble. This is counter-intuitive to most people as it would seem that the tailgate acts as a big parachute back there. This is simply not the case.

Of course there are many variables in the equation including overall vehicle aerodynamics, vehicle speed, altitude, etc. but the principle is sound.

Found this image:
 
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Old Jun 8, 2011 | 12:15 PM
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All things being equal I'd say regen?
 
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Old Jun 8, 2011 | 01:12 PM
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I have heard the bed cover doesn't make any difference either. In 150 miles you have a lot of variables. Slow drivers you passed,did you use cruise control the whole time,even a small head wind. Your only talking 1 mpg,you said 18 or 19 to 16 or 17. If you drop more I would get concerned.
 
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Old Jun 8, 2011 | 01:34 PM
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I did have a regen at the beginning of the trip but, usually the mpg after that recovers to near normal after a trip of 100+ mi.

I forgot to mention however, I noticed more whipping around when passing 18 wheelers of which there are plenty of on I80.

I wonder if that was more pronounced because of the bed cover being rolled up and causing a more disturbed air flow in the bed and around the truck.

In any case, I will put the cover out and I have to make the trip again Fri. I will be interested if things are back to normal.

I love this truck and want to know everything that makes it the happiest.

LOL, a lesson I should have learned a long time ago with my other half.
 
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Old Jun 8, 2011 | 01:42 PM
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Originally Posted by Noah2010
I did have a regen at the beginning of the trip but, usually the mpg after that recovers to near normal after a trip of 100+ mi.

I forgot to mention however, I noticed more whipping around when passing 18 wheelers of which there are plenty of on I80.

I wonder if that was more pronounced because of the bed cover being rolled up and causing a more disturbed air flow in the bed and around the truck.

In any case, I will put the cover out and I have to make the trip again Fri. I will be interested if things are back to normal.

I love this truck and want to know everything that makes it the happiest.

LOL, a lesson I should have learned a long time ago with my other half.

Did you have regens on your other trips?
 
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Old Jun 8, 2011 | 01:43 PM
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Check these out and come to your own conclusion:

YouTube - ‪Truck bed test, open bed‬‏

YouTube - ‪Pickup tailgate down, air turbulence‬‏

YouTube - ‪Truck bed test, tonneau cover‬‏

All things being equal (including regens), which has the least drag?

And finally, any questions as to why towing kills mileage?

http://www.youtube.com/watch?v=pcOthVT-PlA&NR=1
 
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Old Jun 8, 2011 | 04:47 PM
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Originally Posted by EpicCowlick
...And finally, any questions as to why towing kills mileage?

YouTube - ‪Example of high wind resistance‬‏
Looks like the bicycle on the roof rack kills a little too.


There could be other variables at work with the subject trip. A little headwind or crosswind not present on other trips, or something like that. Driving into even a mild headwind kills 2 or 3 MPG on my '11.

Windshields on modern trucks have a flatter angle (and probably better aerodynamics) than they did on older trucks, so that probably affects how the "bubble" in the rear works, and why the old tailgate down trick doesn't work on newer trucks like it seemed to with older trucks.

I remember trying various things with my '05 when I first got it. Tailgate down did indeed make the mileage worse. Hard tonneau made perhaps a slight improvement over no tonneau. Cab-high topper made a 1+ MPG improvement over the hard tonneau or bare box. Just my results as I remember them.

Joe
 
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Old Jun 8, 2011 | 07:53 PM
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Did you have the tranny flash?

I have my truck in the shop now for the same issue
I went from 18.2 to 15.2
Ford said there is nothing wrong

But i went months at 18 then after tranny flash 2 weeks later i noticed it was going down. I reset and have been averaging 15 sense.


I get regens every 100 to 150 now
Ford says 100-500 miles is normal
But i have been going 400-500 sence it was new. Now 100-150

I hate dealers and Ford help line people
Well maybe you are driving differant! No i am not even if i was it should not drop 3 MPG.

We dont know what it is but it seems normal
 
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Old Jun 8, 2011 | 08:16 PM
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another little thing you might not of noticed, chevy came out with it first, but if you look at the top of the tailgates on most of the new trucks you will see either built into the metal or installed as a plastic tailgate cap, it will protrude past the top of the tailgate and have an over hanging lip going back of the tailgate cap

.

the top of the tailgate on this new dodge shows what I am talking about. that isn't there for styling its done to help the airflow past the truck as it goes over the tailgate, even the top back edge of the roof on some vehicles has a similar shape. some thing it might yield .5 mpg
 
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Old Jun 8, 2011 | 08:57 PM
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Epic is right. Think airfoil in terms of lift and decreasing weight.
 
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Old Jun 8, 2011 | 09:56 PM
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I think the Mythbusters did a segment on gate on and gate off. If I remember correctly, gate up improved the mileage.
 
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Old Jun 8, 2011 | 10:26 PM
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Yea, they did awhile back and gate up is what I remember also because that allows the air bubble to form which allows additional air to flow over the bubble.
 
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