Do roof rails (w/o cross rails) affect MPG gas mileage?

gsxr6mt · Feb 23, 2014

Hi, I've searched the internet and found a lot of convincing evidence that crossrails or larger things against headwind will affect gas mileage by 5% or more.
My question is more about roof rails ONLY. Has anyone installed this aftermarket honda accessory (only) and noticed a decrease in MPG? We have a 2014.

We intend to use one of these roof bags on an as needed basis when travelling: WeatherTech RackSack Rooftop Cargo Bag Carrier | WeatherTech.com which is great because it can be removed right after the road trip so it's just a temporary drop in MPG.

But obviously, we need roof racks installed to make this work, and the the roof racks are not temporary! Does anyone have a link or info on if rails are a drag?

Thanks!

richrob08 · Feb 23, 2014

Get a hitch mounted carrier and don't worry about it. If you must use a rooftop bag, side rails don't have to be permanent. If you can install them aftermarket, you can always remove them.

gsxr6mt · Feb 23, 2014

richrob08 said:
Get a hitch mounted carrier and don't worry about it. If you must use a rooftop bag, side rails don't have to be permanent. If you can install them aftermarket, you can always remove them.

I thought of this, but it's a major cost difference ($150 for the OEM rails, vs $400+ for, hitch, wiring harness,etc)...why go for the higher cost if it ends up roof rails alone don't affect MPG. The installation of the Honda OEM Roofrails requires cutting of the roof moldings, so post removal exposes bolts and other areas underneath the roof moldings....did you have another aftermarket roof rail you were referring to whihc can be installed and removed w/o making permanent changes to the odyssey?

OdysseyTE · Feb 23, 2014

Roof rails will not effect MPG, cross bars may to some degree and mostly is not only while traveling at a freeway speeds. If most of your driving is freeway and you're worried about 2mpg then take the cross bars off when not in use.

richrob08 · Feb 23, 2014

You could get hitch set up for about 200$. No other side rails I am aware of but I haven't checked. You could also get Yakima or Thule towers and just not install the cross bars. They mount flush on your roof between the doors. They might be pricier than side rails too though but atleast are not perms art and no ugly bolts to deal with.

davedrivesody · Feb 23, 2014

Agree roof rails won't affect fuel mileage. They have no effect on the van's aerodynamics. And they look good from the side IMHO.

RGJMINI · Feb 23, 2014

I just had the OME version of the rails and cross bars installed two weeks ago. I track my fuel mileage each fill up and haven't noticed any effect yet. I'm going to track the mileage over a greater period of time to see what effect the cross bars have. Given the shape of the Weather tech roof bag, I can see it killing mileage. Thule makes some very clean looking aero shaped roof containers but they are quite a bit more money than the WT.

RGJMINI

0dyfamily · Feb 24, 2014

OdysseyTE said:
Roof rails will not effect MPG, cross bars may to some degree and mostly is not only while traveling at a freeway speeds. If most of your driving is freeway and you're worried about 2mpg then take the cross bars off when not in use.

I've put cross bars on two different Odys with no measurable effect on MPG. Measured fuel consumption on a number of road trips before and after cross bar installation. If there is a difference, it's in the "data noise" (i.e., well inside one standard deviation).

OF

mgkg3 · Feb 24, 2014

Drag due to adding roof rails would be negligible and how you drive and road conditions will have a greater impact. Cross bars is also negligible but both will technically reduce MPG.

The rails has openings that perturbs the flow over the roof and create localized adverse pressure gradient that adds to the drag but its quite small, in all likelihood. The crossbars, depending on its shape (cross section), may or may not be a big deal. The best type would have rounded leading edge and probably flattened oval shape or very thin arch. The worse would be rectangular shaped crossbar.

The recommendation of putting luggage using tow hitch is probably the least impacting way to carry andy luggage outside the vehicle since the airflow behind the rear section is already separated and is draggy, so to speak. Anything on the roof, like the link you've provided, is quite bad. The use of more slender shell on the roof top would be better, but clearly the inside the vehicle is best.

Cheers!

ps, I'm aeronautical engineer...

kenobee · Feb 24, 2014

Try this one out-
]Rola 59004 Airfoil LG Black Roof Top Cargo Box : Amazon.com : Automotive
I have the longer one and although it does affect MPG, it is one of the more aerodynamic ones without getting too pricey. it also is pretty quiet for a carrier. the nice thing is it is lockable and more impervious to weather as well. The more streamlined Thule ones are pretty expensive. I use the Whisbar cross bar and notice no difference in MPG on the two vehicles I use them on. The OEM cross rails appear to be fairly streamlined and are fairly inexpensive as well. I went away from the hitch bag/carrier as I like easy access to the back of the car, and the roof carrier doesn't affect length when parking. When I had our Rola carrier on out 2012 ENCLAVE, which is a taller car, with OEM cross rails, the clearance was just under 6'6", so still able to go through car wash, parking garage, etc.

richrob08 · Feb 25, 2014

They make swing away hitch mounted cargo carriers so getting to the lift gate is a breeze. Rola even makes one. http://www.summittrailers.com/images/r_level/rola_59109.jpg

I have tried both roof and hitch mounted carriers. I prefer the the hitch mount for easier loading/unloading. No having to open doors and step up into the van floor to get to things loaded in the roof box. I even installed running boards but often times still does not give me enough reach and if you've ever had to fetch anything from a roof box during a road trip in the winter with your kids trying to sleep, they and your wife won't be happy with you letting all the cold air in.

Also, hitch boxes aren't tapered like roof boxes so they have a more regular shape, which to me also makes loading easier. Most hitch boxes also come with full light kits too for better visibility. License plates can also be relocated onto the cargo box. Yes, it adds to the length of an already lengthy vehicle but the only time I ever notice is when I'm backing up and even then, it's still pretty easy to back up especially if you have the backup camera to remind you it's back there.

bellevue260 · Feb 25, 2014

Any effect on MPG will be negligible at best. I have the roof rails, and crossbars, I remove the cross bars when not in use, they are annoying when you need to clear snow or wash the roof. Eventually I will pony up for the hitch when its time for bikes and I already have a few platform racks to use...I got the oem rails, because there were no aftermarket products from Thule or other mfrs, like I have on my Accord, we have a big box that we use for vacation. Again, the fuel drain is negligible even with the box, and you likely use the box or bag only a few times a year anyway, so its not costing that much more in fuel consumption anyway...

0dyfamily · Feb 26, 2014

You know what...I'd tend to agree with all of the above. When I installed my aero-profile crossbars, that was at a time when I started paying more attention to how I was driving, trying to get better MPG.

Makes me wonder if one set of factors (my adding crossbars, thus driving down my fuel economy) was offset by my trying to act more like a granny on the throttle (increasing fuel economy).

When OdysseyTE says that 2mpg figure, it seems I've read that too somewhere before where someone actually measured it. It certainly sounds believeable that some crossbars alone could be worth as much as 2mpg at healthy freeway speeds. I mean, they're a pair of big pieces that span the entire width of the roof. Like mgkg3 said, it's gotta make a difference, putting extra stuff on an otherwise "clean" top.

OF

Konos · Feb 26, 2014

Agree with everyone here cross bars you will never notice. On my old Tucson I left the crossbars on - no difference in fuel consumption. Even with the sport rack box on the roof it was only a 2-3 MPG hit on the highway.

Ninexapple · May 21, 2018

Roof Rails alone will not decrease MPG. If you put stuff up there, it will, and the noise will validate it.
Crossrails will affect MPG slighty, and they are NOISY ass hell

Do roof rails (w/o cross rails) affect MPG gas mileage?

gsxr6mt

richrob08

gsxr6mt

OdysseyTE

richrob08

davedrivesody

RGJMINI

0dyfamily

mgkg3

kenobee

richrob08

bellevue260

0dyfamily

Konos

Ninexapple

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