Roof racks suck gas, but how much?

Paddy

Adventurer
Any data on this? I'm pretty sure a roof rack is one of the most efficient ways to reduce efficiency, which is unfortunate because they are obviously a very handy thing to have. I have experienced this in other rigs, but now that I have a sprinter I'm curious what damage it will do to my lovely 26mpg vans economy?
 

JIMBO

Expedition Leader
:sombrero: You must make a trade, or go without additional storage/equipment carrying ability--suptoyou

Mine is quiet and no measureable mileage difference-

:costumed-smiley-007:wings: JIMBO
 

Paddy

Adventurer
I'm planning on making my rack actually just two rails and use the smooth roof as the base so it will suck minimal fuel and make minimal noise. I have doubts that your mileage decrease isn't measurable though.
 

JIMBO

Expedition Leader
:sombrero: Probably could be measured, but-


I'm planning on making my rack actually just two rails and use the smooth roof as the base so it will suck minimal fuel and make minimal noise. I have doubts that your mileage decrease isn't measurable though.

Not under normal ops/conditions

:costumed-smiley-007:wings: JIMBO
 

huskyhauler

Adventurer
Generally the rule of thumb, is the smaller the motor and smaller the size of the vehicle, the more of an affect a rack will have on pushing the added mass through the air. The larger the vehicle, the less the added size affects the motor's ability to propel it through he air. On a small honda, a roof rack will shave off noticeable mileage. On my ambulance a roof rack will be negligible.
 

Paddy

Adventurer
But what is negligible to you? I feel like some people think 2-3mpg is negligible but for me that's a lot. I feel that a roof rack is a minimum of minus 1 mpg on anything short of a tour bus. This is for hwy speed of course, low speeds don't matter as much so an off road only rig, sure, rack it up. It's not the mass either it's the wind resistance. Of course even my streamlined rack idea will have plenty of resistance when we put the gear up there.

I hear you on the motor size. On my old Subaru it drowned it, but the sprinter is much bigger. Is it big though? It's 5000lbs and has a 2.7L engine although for its size the thing seems to have lots of power.
 

ujoint

Supporting Sponsor
I'll be installing our 3rd prototype rack on V7 this week, which is still 100% stock so I'll be able to get a good estimate on MPG loss. This rack is super low profile so I don't expect a big change. But, it will if you bolt a bunch of bulky stuff to it....

We've had 2 of these racks on vans since May and both put down a ton of miles (and some abuse), neither has given me any feedback on noise. Both 7.3's, regular body vans on 35's. I think the noise isn't noticeable because the racks aren't full length. V7 is gas so I'll be able to hear noise easily.

11109596_969499076402654_1907329586197852850_n.jpg
 

Stumpalump

Expedition Leader
My high top van gets the 12-13 mpg with the V10 and that is as good as anybody else with a pop top or no top. I think the reason the mileage is OK is that the top is sloped and aero dynamic. This makes me think that an air dam on the front and smooth sides on a roof rack would help it.
 

Flyinbronco

Observer
When I run my Defender roof rack on my F350 super duty I'll lose 1-1.5 MPG. I attribute most of the drag on the 4 8" KC lights mounted across the front.
 

simple

Adventurer
From my experience you can bet on a 1-2mpg drop for just the rack without anything piled up on it. :sombrero:
 

Stumpalump

Expedition Leader
I'll be installing our 3rd prototype rack on V7 this week, which is still 100% stock so I'll be able to get a good estimate on MPG loss. This rack is super low profile so I don't expect a big change. But, it will if you bolt a bunch of bulky stuff to it....

We've had 2 of these racks on vans since May and both put down a ton of miles (and some abuse), neither has given me any feedback on noise. Both 7.3's, regular body vans on 35's. I think the noise isn't noticeable because the racks aren't full length. V7 is gas so I'll be able to hear noise easily.

11109596_969499076402654_1907329586197852850_n.jpg
Dang that's so nice it needs to be on every page of this thread. Bump
 

jjohnny350

Adventurer
I agree with smaller engine smaller car is effected more by a rack. Larger vehicles with larger engines not as effected. I think that pretty much sums it up. Here are some of my numbers and experience with it, I love roof racks and how much more useful they make vehicles. I have had a bunch of racks on lots of different vehicles. Here are some numbers of how it has effected mpg and noise.

Honda civic, gutless 4 cyl, rack with no bikes on, 2-5 mpg drop, some noise, not much, less noise with a wind deflector in front, more of a hum with no wind defelector.
Honda civic, same gutless 4 cyl, rack with 2 bikes on top, 4-8 mpg drop.

Nissan maxima, v6 good torque, 2 bikes on top, 2-4 mpg drop.

e350 5.4 v8, ujor 6" 35" tires, empty rack, less than 1 mpg drop, wind noise in front, and noise from rack metal on rack when hitting bumps. Have full expanded metal floor.
e350 5.4 v8, ujor 6" 35" tires, rack full of gear, 1-3 mpg drop, only 3 if have big wind deflecting things up there.

I cant offer much help on a sprinter as they are much different than a ford gas van. Seems like a large vehicle with a medium sized engine. I have talked to 2 people with sprinters and they said they noticed a 3-6 mpg difference depending on how much gear is up there.
How fast you drive I think makes a big difference too, I usually drive 10 over the speed limit but when Ive slowed it down that seems to help a fair amount also.
 

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