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So how much do thule cargo boxes ruin gas mileage?

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steezyjibber
Posts: 15967 - Karma: 11,026
so i've heard contradicting stories so i'm resorting to NS to get some ideas. i was thinkin of throwin a thule box on my 03 subaru legacy sedan this winter. so here's my question for anyone who has one. please state your year & car model (not that it really matters i guess but i'm interested), and the MPG you lose by having a box on the top. and also if you'd recommend a box, or if it's a waste of money.

thanks
Aug 2 2010 12:33PM
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RenegadeZ3
Posts: 452 - Karma: 38
Legit question. I'm pretty OCD about stuff like that, so I do those kinds of nerdy calculations. On the highway, the difference is about 28 mpg without the box vs. 23 with it. I only throw the box on when I have 4 people. And it's a 2003 A4, with one of Thule's pretty aerodynamic boxes.
Aug 2 2010 12:38PM
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hokkanee
Posts: 1800 - Karma: 435
I have an 08 tahoe and the mpg goes from around 15 to 13 when the box goes on. I love the added storage and would recommend one especially if you drive a lot of people to the mountain
Aug 2 2010 12:46PM
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BVT802
Posts: 443 - Karma: 18
I have one on my jetta and I notice a decrease between 5 and 6mpg depending on the number of people I am taking with me. I leave mine on regardless of it's just me or if it's me and some buddies. Regardless its a pretty sick thing to have on your car to keep things protected from the elements and leave more space for you and your buddies to stretch out.
Aug 2 2010 1:06PM
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chipkalback
Posts: 2255 - Karma: 30
I have an '08 Outback XT with a Thule Atlantis 1800 on top for about 8 months out of the year, and I average about 19-21 MPG using premium gasoline. After having used ski racks for years, I'm now convinced a cargo box is the only way to go, regardless of how many people are in my car. The dirt and grime you notice all over your skis, and in your bindings, when you use a ski rack is virtually nonexistent when you've got your stuff stored in a cargo box. They're also great for summer camping trips, etc.

Make sure if you're going to get a cargo box to go with Thule, NOT Yakima. Thule boxes are designed much smarter IMO, and they're tested on the autobahn and have no speed limit, whereas Yakima boxes are rated only to 75MPH max, as well as have a history of the lids blowing open. The Freeskier guys can attest to that as a few years ago their Yakima box blew open driving up I-70 and they lost a bunch of gear.
Aug 2 2010 1:17PM
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A-dub
Posts: 129 - Karma: 13

Good question,, just been on a 2000 mile round trip to the glaciers in france in an '-5 Ford Focus.

Think looking at bills its cost about 5mpg on motorway driving. The benefits over a roofrack are amazing though. Thule are rated at about 75kg load so we had 5 pairs of skis, all our boots and then back protectors in which really free'd up space in the car and made it a relatively comfortable drive.

The other great thing with the Thule system is that it takes literally 2 minutes to get the box off and maybe 5-10 mins to take the bars off each time so it really isnt that much of a hastle if you want to save on gas when you're not using it. Buy one, you wont regret it!

Aug 2 2010 1:31PM
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Mike.Records
Posts: 1311 - Karma: 756
My Jetta Wagon goes from 29.5with nothing on the roof to 27.5 with a box.
Aug 2 2010 3:20PM
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grown-ninja
Posts: 3031 - Karma: 175
all my thule stuff was one of my best purchases in a while, browsed cl and got all my stuff for about 150 bucks would have been 350-400 new.

the little decrees in gas millage is well worth the amazing convenience a thule provides
Aug 2 2010 3:26PM
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Fuck.W.M.E.
Posts: 84 - Karma: 14
My 2002 sequoia goes from 19-17.5 with dub rocketboxes. Definitely worth the space and steezefactor duuuhzzz
Aug 2 2010 4:22PM
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WinterStick
Posts: 234 - Karma: 100
So from the average results, it looks like you're losing around 3 miles per gallon with the box. However, you get to fit a fourth person in the car as opposed to just having three with a seat folded down.

Let g be the number of gallons used on a trip.

So g = distance/observed miles per gallon = d/m

Let p be the number of passengers who can fit

So having a box is efficient if the gallons used per person on a trip are lower than if not using the box.

So, gallons used without the box per 3 passengers > gallons used with the box per 4 passengers.

g with box = d/m
g without box = d/(m-3)

(d/m)*(1/3) > (d/(m-3))*(1/4)

So as long as you are observing more than 12 mpg normally, it makes more sense to use a Thule with 4 people. BOOM.
Aug 3 2010 12:18AM
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PC.
Posts: 1105 - Karma: 18
I've Got a roof rack. Thule bars and towers. Inno 6 ski carrier. However I'm considering buying a Thule rack, because I'm not 100% sure on the inno racks quality.
Aug 3 2010 2:58AM
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hanksy
Posts: 659 - Karma: 265
I had a 98 mercedes wagon, lost about 2 mpg with the box on. But the box was definitely an amazing addition to my car. Frees up so much space, you can fit a shitload of stuff up there, and it looks badass. I have a GTI now, but I still have my box and once I have money for new towers I'm throwing a box up there for the winter.
Aug 3 2010 8:53AM
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Reed.
Posts: 4489 - Karma: 272
the best part about a box is the safety factor. You can leave your stuff in it overnight/however long without worrying about skis being stolen. Less road salt/grime on your skis is also really nice.
Aug 3 2010 6:29PM
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broto
Posts: 9039 - Karma: 25,662
i lost you here
Aug 3 2010 11:22PM
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eheath
Posts: 61590 - Karma: 122,949
I have one of the really newer thules from like two years ago thats pretty flat and i get 30mpg on my 05 legacy.
Aug 3 2010 11:29PM
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Peter.
Posts: 23796 - Karma: 13,014
someone's a math major
Aug 3 2010 11:43PM
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