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Do Truck Caps affect gas mileage?

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#1 BrokenRod

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Posted December 17 2004 - 5:03 PM

I'm planning to put a cab-high truck cap on my GMC xcab this spring. Anybody ever done a comparison of the before-after affects of the cap on fuel consumption?
Thanks, BR

#2 Sandflee

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Posted December 17 2004 - 5:25 PM

i would say i depends, did u have a top for the bed or was it open? if it was open i would guess you'll have the same Gas Milage, trading additional weight for less drag on the tailgate

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#3 BrianBM

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Posted December 17 2004 - 9:41 PM

I assume "cab-high" indicates that the cap will be above the roof of the cab. That being so you will probably see some loss of mileage - but I'm guessing and hope someone steps in who KNOWS. A cap that is flush with the cab top improves drag enough to make a difference, for the better.

#4 Backbeach Jake

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Posted December 17 2004 - 10:30 PM

I gained 2-3 mpg with mine, same height as the cab.


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Posted December 18 2004 - 1:32 AM

Caps certainly make a difference in MPG. If you are running a pickup without a tonneau cover, the addition of a cap that is the same height as the cab will improve your gas mileage. I remember seeing an article comparing several caps, and there was variation between them. The one that got the best mileage was the same height as the cab, and fit very closely behind the rear window. As a matter of fact, I believe there was a replacement window made by the same manufacturer that slid from side-to-side, so you could access the rear from the cab. Sorry I don't remember which magazine it was in! If I run across it (I never throw ANYTHING out) I'll get back to you. Perhaps CONSUMERS DIGEST did a similar review?