| MesaBeige |
| Any of you engineering types out there have an idea of the impact to gas mileage with the roof rack. |
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| DaleB |
quote:
Originally posted by MesaBeige
Any of you engineering types out there have an idea of the impact to gas mileage with the roof rack.
Should be N/A as long as you don't put anything on the rack. |
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| MesaBeige |
| 75% of my driving is long-trip highway driving so I (not an engineering type) am thinking there should be some impact due to turbulence. |
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| DaleB |
quote:
Originally posted by MesaBeige
75% of my driving is long-trip highway driving so I (not an engineering type) am thinking there should be some impact due to turbulence.
Anything can be considered an obstruction to what is thought to be normal air flow.
And yet, a well designed spoiler working inside the airflow can actually reduce the resistance vs. no spoiler at all.
Given the air-foil like shape of the rack I would suspect it's quite slippery as it goes through the air.
The same goes for any factory roof rack on a production vehicle which would have to show minimal affect to the overall vehicle's coefficient during wind tunnel testing, in order to meet CAFE requirements for the published EPA rating. |
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| Sinecure |
Try taking it off and report back on the results.
I know that adding a ski rack (without skis) to a car typically kills 1-2mpg. The roof rack on the MDX isn't nearly as draggy as a ski rack, but I'm sure it makes some difference.
If it were easy to remove, I'd do it. But I use it for my roofbox sometimes, so I keep it there. |
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| msu79gt82 |
quote:
Originally posted by Sinecure
Try taking it off and report back on the results. ... If it were easy to remove, I'd do it.
First MesaBeige; welcome back Old-Timer :D
Second, I removed the roof rack on my old '01. It is easy to do, however you will need a pair of full-lenght channel covers if you intend to leave it off. |
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| G. COLTON |
quote:
Originally posted by MesaBeige
75% of my driving is long-trip highway driving so I (not an engineering type) am thinking there should be some impact due to turbulence.
You are correct. There is turbulence generated by the structure of the roof rack. I have never seen any wind tunnel nor real life figures on the loss in fuel mileage, but there will be some.
I would expect it to be in the 1/2 mile per gallon category, possible slightly less.
It would take a very sofisticated experiment for an individual to measure it on their own.
This is just like driving your vehicle with the windows or sunroof open. This also cuts the gas mileage. However, when the weather is nece I like to have these open.
G |
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| mgmdx |
quote:
Originally posted by DaleB
Should be N/A as long as you don't put anything on the rack.
This is definitely true. :4:
I have a Yakima roof rack on my MDX that I keep on all the time. It has 3 bike carrier attachments (in the spring, summer, and fall) and a ski carrier attachment (in the winter). The mpg difference of having the roof rack and/or attachments on is negligible. Where you really see a big mileage drop is when you carry large items on the roof that create large wind resistance area.
For example, carrying skis on top does not significantly affect the mpg, while carrying 3 bikes on the roof definitely creates drag and significantly reduces the gas mileage.
On a recent trip to Pismo Beach (app. 230 mi each way) our MDX was fully loaded with stuff, including 3 bikes on the roof. We drove most of the way with AC blasting, and although most of the trip was all-highway, I barely managed to average 16.5 mpg (I think the use of AC played a significant role, as well as venturing out into the sand dunes for some fun driving). In comparison, similar length highway trips to Lake Tahoe in the winter (app. 200 mi each way), with skis on the roof of our MDX result in approximately 22 average round trip mpg. |
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| MesaBeige |
Thank you one and all!
The channel covers cost $85 with tax.
At 1/2 mpg savings, $2.50 per gallon and an average of 18 mpg, it will take me forever to make up the $85 difference.
The rack on stays on.
RACK ON! |
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| highcountrymdx |
Let's say you drive 15,000 miles/year @18mph (with roof rack). At $3/gal, your fuel cost would be $2500. If you removed the rack, and averaged 18.5 mpg, your annual fuel cost would be $2432. Payback to replace the rack (@ $81) works out to be a bit over 14 months. If you kept the X for 5 years, your net savings totals about $260.
You can beat this discussion into the ground, but $260 is $260. BTW, I removed my rack to more easily clean/wax the roof. I may also be a bit quieter, but who knows. |
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