Roof racks suck gas, but how much?

[Paddy]

Look up speed rail fittings for an easy DIY solution that might yield better results than plastic.

 

[mikracer]

Is the consensus that a fairing helps or hurts gas mileage? I plan on installing a Yakima megawarrior towards the rear of the van and have the fairing. Just not sure if I need it.

 

[fog cutter]

Look up speed rail fittings for an easy DIY solution that might yield better results than plastic.

i assume he meant for the fairing itself rather than attachments to the rack.

i would use either a ready made fairing from Thule or Yakima - or get a piece of 3/16" PVC sheet from the local industrial plastics supplier. it sands well through different grades of grit and can be polished with Novus system. http://www.novuspolish.com/ http://www.modernplastics.com/products/flametech-fm-4910/

 

[jjohnny350]

I think fairing helps, seeing semis with similar things on the top of their cabs and now under the trailer, I can only think it would help to make it more aerodynamic.

 

[landyachtcaptn]

On a big box of a van the fairing doesn't make any noticeable difference in milage. I have one on my rack for 2 reasons: 1. Noise Reduction (My roof rack sounds like there is a jet engine up there if I don't direct the air over it) and 2. To direct branches,limbs and other overhead obstacles smoothly over the rack without getting caught on it and risking bending it.

 

[Paddy]

No I meant for a rack solution that doesn't require welding. Beats abs, possibly.

 

[huskyhauler]

Edit: major overhaul

A fairing only helps with MPG if it contributes to the overall aerodynamics of a vehicle with it as opposed to without it. Simply adding a fairing to a roof rack system on most consumer vehicles is only good for noise a reduction solution, not as a drag reducing solution. The reason is adding a roof rack with cross bars causes increased drag, and while a fairing may help diffuse direct air around the cross bars and decrease associated noise, the fairing itself still contributes to increased drag as it defuses air around the cross bars but it does little to direct the dispersed air along the vehicle and pass it along smoothly at the rear.

Another side affect is if you are not careful about keeping your car clean and waxed the fairing will chew up your paint where the feet of the fairing meet the roof, even with the pads.

With that said, new roof rack systems have cross bars designed to eliminate whistling and reduce noise. I don't know that Yakima or Thule sell fairings anymore.

 

[chet6.7]

The leading edge of the camper,and lowest horizontal bar are fairly free of bugs.The vertical bar starts showing bug hits as it rises,the top horizontal bar gets a lot of hits.I suspect that a rack that was lower than the pressure wave coming over the cab would not make a big difference in mileage,at least when the rack is empty.

 

[Cole]

I've got a Long/tall Sprinter with 14' of Yakima rack on top. 4 cross bars, cargo box, and MaxxFan. So, I'll chime in here. But, honestly, you either need a rack or you don't. :coffeedrink: If I can't bring my stuff with me, then it defeated the whole point of the van.

My Sprinter is also a dually with tires 6" larger than stock, and GDE Eco-tune. ~3:73 great ratio.

I've tracked my mileage for the last 16,979 miles. The high is about 25mpg and the low around 18mpg. (My real mpg is higher as my speedo is off with the big tires)

Adding the rack didn't make a noticeable difference. It was on the van with cargo box, and fairing when I did my highest mpg run doing 75mph+ on high mountian passes (10-12k feet. This was also over a 250mile trip that included in town driving and running the diesel furnace.

The only thing that seems to matter on the Sprinter is how and where you drive it. MPG drops significantly above 65mph, even before the rack, tune and tires. Burning the diesel furnace eats up diesel and effects mileage readings, we run the furnace a LOT.

I got 18mpg with another van on a trailer (7,000lb) behind my Sprinter (and roof racks) while doing 80mph across country.

Splitting hairs about the mileage of a Sprinter is kinda silly IMO when you look at what other vans get. Load it up with your toys and go hve fun!

As you can see, the paddle boards take up too much room no should be in the roof to camp! You either need a rack or you don't.

 

[Paddy]

Well, it depends on what one considers splitting hairs. I believe some vehicles can suffer as much as 5mpg with a rack, that's not a hair. If sprinter is less affected, then great! However I still want to be mindful of the economy because I love that the van gets 25 and I want to keep that on my side. So for me, I'm putting reinforcing on the inside instead, and make the roof walkable with low profile tie down points rather than a full rack. If nothing else it will look cool.

 

[Cole]

Well, it depends on what one considers splitting hairs. I believe some vehicles can suffer as much as 5mpg with a rack, that's not a hair. If sprinter is less affected, then great! However I still want to be mindful of the economy because I love that the van gets 25 and I want to keep that on my side. So for me, I'm putting reinforcing on the inside instead, and make the roof walkable with low profile tie down points rather than a full rack. If nothing else it will look cool.

My bicycle gets the best MPG of anything I own!! But it doesn't carry two motorcycles, 2 paddle boards and sleep 5 (dogs included) comfortably on a cold rainy mountain night. :coffeedrink:

Show me another vehicle that does what the Sprinter does MPG vs. Utility.

It's completely "splitting hairs" when you are talking (at the wide range) 25mpg vs 20mpg......when other smaller vans get 5-12mpg when trying to do the same thing!! Kinda like bitching that your Prom Queen date has to be home the same time everyone else date does.

My truck got 5-10mpg, so I don't worry too much when my Sprinter is sucking wind hauling a trailer and only getting 18mpg

 

[Cole]

So for me, I'm putting reinforcing on the inside instead, and make the roof walkable with low profile tie down points rather than a full rack. If nothing else it will look cool.

FWIW, the weak link in the Sprinter roof is the body seams. They tend to split open just enough to leak rain inside. The roof will hold the weight fine, but eventually it leaks....bad! So find a good way to address the seams and you should be good.

 

[Paddy]

Yeah man, you don't have to extol the virtues of sprinter on me, It sure wasn't for the off road performance! I have just ruined more than my share of economy in vehicles over the years in a number of ways and some are less necessary to me than others.

My thought is to glue and screw 1/2" plywood underneath the roof in sections, and then insulate over that. Should stiffen it enough and still weigh a lot less than an actual rack. It will only hold two kayaks most of the time anyway. Maybe 1/4" ply would work?
Thanks for the tips on the seams, leaks are a bad thing especially in my climate.

 

[boardrider247]

My bicycle gets the best MPG of anything I own!! But it doesn't carry two motorcycles, 2 paddle boards and sleep 5 (dogs included) comfortably on a cold rainy mountain night. :coffeedrink:

Show me another vehicle that does what the Sprinter does MPG vs. Utility.

It's completely "splitting hairs" when you are talking (at the wide range) 25mpg vs 20mpg......when other smaller vans get 5-12mpg when trying to do the same thing!! Kinda like bitching that your Prom Queen date has to be home the same time everyone else date does.

My truck got 5-10mpg, so I don't worry too much when my Sprinter is sucking wind hauling a trailer and only getting 18mpg

I really don't understand your argument.
Just because a different vehicle gets worse mileage that means we shouldn't be concerned with it????
A 25 to 20 MPG drop is 20%. That trip that was going to cost you $1000 now will cost $1200 in fuel.

While I agree that you either need a rack or you don't. It still seems worthwhile to minimize the affects on MPG when using the rack if possible rather then just blowing it off by saying "well I have a sprinter that get's better mileage then that semi so who cares about the MPG's I'm losing"

:sombrero:

EDIT: Oh and a truck that was only getting 5-10 MPG. OUCH!! No wonder you aren't worried about you mileage damn near anything is an improvement.

EDIT #2: Anecdotaly (SP???) I have noticed no significant drop in MPG when I have surfboards on my load bars. But did notice a drop when I had a RTT up there. So obviously what you have on the rack plays as a big a role in mileage as the type of rack.

 

[Cole]

I really don't understand your argument.
Just because a different vehicle gets worse mileage that means we shouldn't be concerned with it????

It means that fuel mileage shouldn't be judged as an absolute but rather by what a vehicle is and does.

Either you need the utility of a rack or you don't. It's not really a fuel mileage issue, rather a utility issue IMO.


The Yakima rack rails are aluminum and super sleek. No higher than the stock roof ribs. Notice that there are two sets of tracks on this roof. Not sure why anyone wants to add a bunch of extra weight when something like this already works well. The cross bars can be moved anywhere and removed in 5min if you don't need them.

EDIT: Oh and a truck that was only getting 5-10 MPG. OUCH!! No wonder you aren't worried about you mileage damn near anything is an improvement.

Which is honestly what many of the campervans on these forums probably get with their big engines and tons of weight added on.