Does roof rack reduce mpg

- On all my DDs ive had, I always run a roof rack. Remove any roof-racks  I have a roof rack for my Honda Fit which I love, but the drastic impact that rack has on my fuel efficiency for that car is just unacceptable for long trips. 8t Passat estate that generally returns around 35-36 mpg on a fast motorway cruise. The easiest solution to this problem is to remove the roof rack when it's  I want to have a roof rack on my golf but I've heard it can reduce mpg anywhere from as little as 2% mpg all the way to 50% depending on the car. Keep in mind that a car filled with people and cargo will also have an  29 Apr 2016 Moreover, use of roof racks is projected to increase given national travel trends. The car is a 1. I would imagine that you will lose a little bit of gas mileage, but it will not be too bad. e. Im loving my mk2 now that its actually running, but of late, ive become obsessed with its fuel economy. Because it generates aerodynamic drag, a roof rack can sharply increase fuel consumption. What Car?'s acclaimed True MPG real-world fuel economy tests show what sort of MPG you can really expect from your car. Member. 7 May 2013 Roof racks systems can do a lot more than just carry bikes or canoes - they can turn a Toyota Prius into a virtual Toyota 4Runner - with much better mileage. expert reply by: Jameson C. With an empty rack, no mpg hit. I too noticed an increase in gas mileage on my old and long since gone small Hyundai Elantra wagon when I topped it as well. Moreover, use of roof racks is projected to increase given national  15 Apr 2015 Yes, Roof Boxes And Ski Racks Really Do Cut MPG—More Than You Might Think. Yes it will lower you MPG but not by that much maybe 1% to 2%. specially the rails - no bars or load etc. Reduce aerodynamic drag  Drivers can also increase fuel efficiency by minimizing transported mass, i. 5mpg. 11 Mar 2013 I have a Silverado with a camper shell. As mentioned above, when travelling at speed close your windows and sunroof. im not going to be putting a spare up there and hardly ever luggage. That's not just a problem for your wallet but possibly for the  1 Jun 2006 We are considering buying a Prius, but would need to install roof racks for transporting bicycles. (Toyota Yaris subcompact, 30/37 MPG; Ford Explorer, 20/28MPG - and mileage leader in its class). It will not be a large heavy duty rack. I take the roof racks off and put them into the car, and put them back  Once you get to about 30 mph (48 km/h) a car uses more energy to overcome wind resistance than it does fighting rolling resistance. I hope this Our hitch mounted bike rack with 2 bikes on it does not change the mpg. Any idea how much the loss of aerodynamics would decrease my mpg? My youtube  21 Aug 2014 Fuel Consumption: The fairing is going to allow your vehicle to cut through the wind with reduced drag and increase your MPG. 5 percent. Having your sun roof open or windows down can increase drag a little at higher speeds. Even with the fairing. Now that we've established roof racks are a major problem plaguing the nation, let's explore how we can stop them. 5% to 20% mentioned in 2 of the above links). The 2% was reported by a mostly city driver in a Yukon Denali (large SUV) with roof racks. 28 Apr 2016 How to reduce the fuel-economy costs of roof racks. Although a small amount, it will negatively affect your fuel economy. A roof box, bike carrier, or ski-rack can be a real drag on your car's fuel economy. Fuel Cost Savings: $0. What I after is  My '01 Outback has two easily-removable crossbars on the roof rack, which I never use. For a segment Lol, i a pretty sure anything that produces more drag will increase fuel consumption. Roof bars will impact your fuel economy as they adjust aerodynamics and increase drag. But there are ways to minimize Extensive computer modeling and wind-tunnel testing are employed to reduce the coefficient of drag, which is inversely correlated with fuel economy. . is it I drove from Scotland to France with 4 bikes on the roof of my Yeti, it had a very noticeable affect on the high speed performance and on the economy, much more than a roof box. Posted 7 years ago. 3 Nov 2014 if I removed my crossbars, should I expect an increase in mileage? Whether it will offset any mileage loss due to the colder temperatures most of the country is experiencing is open to debate. I don't have numbers to back that claim up but that is about what I lose when I have mine on. The study notes that roof racks can reduce fuel economy by up to 25 percent. Using cruise control on the highway helps you maintain a con- stant speed and, in most cases, will save gas. 30 May 2008 I'll have a Thule roof box on our subie outback for the first time - I think it's about 16 liter size, big enough to handle 4 skis, boots, poles and equipment. ) Drivers get instant feedback on how driving habits affect mileage. leader in automotive rack transport systems. Unused roof racks could lead to a 12% loss in fuel economy. Kidding. The roof box is a long thin  28 Jul 2008 hey folks- going to pick up my 2. 24 Feb 2011 (For related reading, also take a look at 9 Easy Ways To Increase Your Gas Mileage. A drop in your vehicle's fuel economy can be a sign of engine trouble. I want a ladder rack to carry my long boat and to reduce what needs to be stored in my sleeping quarters how much do they effect mpg. Your driving style (how much your brake and overtake) as well as whether you're partial to cool air will affect fuel consumption much more than the  There are many techniques drivers can use to reduce gasoline consumption, improve gas mileage and save money. Normally car does 33 mpg (down to about 30 just now, service due). 28 Apr 2016 That roof rack you absolutely had to have may come in handy now and again, but a new study from Berkeley Lab says that it's also costing you quite a bit of money in lost fuel economy. If you really need one, then MPG is not a factor because, well, you REALLY NEED one. PeterPoddy. Roof racks create drag, which requires the car to exert more effort to cut through the air, wasting fuel in the process. These top tips are tried and tested ideas that really do make a positive difference to your car's fuel economy. 4mpg – Two front windows a third open 30. I have a full roof rack on my 2004 and get 29 MPG on the highway which is  17 Jun 2016 When it comes to hauling camping gear and all the miscellaneous crap you can't fit inside your car, a roof rack is two thumbs way up. Anyone experimented with  I'm considering putting a roof rack on my Transit Connect on which to adhere my solar panel. The roof slope with the racks made the back end of the canoe sit higher than the front. Recently, I drove with an empty (except for some pads) roof rack on the car on the same trip that I make frequently (I needed to use the rack to carry some stuff for a short distance while there). the number of people or the amount of cargo, tools, and equipment carried in the vehicle. It did reduce the noise some, not sure about the gas mileage. So, have a read and start making savings straight away! 10 – Box clever. What's surprising is just how much difference the crossbars between the roof rails make, even with a wind deflector. I have a Thule rack with a fairing, and a medium size roof box. gonefishin. Adding bikes knocked off 4-5mpg. Taking The fuel efficient driving tool is designed to give consumers information about how they may be able to reduce their fuel bill. Ive had a Yakima brand one for years, and just today moved over the gutter clamps, cross bars, and  10 Feb 2011 Putting a fairing on the roof rack will almost eliminate any lessening of fuel economy. Any protuberance on a vehicle's roof, be it a cargo carrier, a kayak, a bicycle, a mattress, or large road kill, will add to the vehicle's wind resistance. I've heard that wing mirrors increase drag by about 25% because of the way they affect the airflow along the  10 Mar 2007 The stated MPG penalty isn't consistent (if it's stated), and when it is stated, it varies wildly (eg. at 105 km/h. so i've heard contradicting stories so i'm resorting to NS to get some ideas. just 4 6" lights like this render i have of it:  Prius or Insight owners with Yakima or Thule roof racks: How much of a hit do you take on your gas mileage just from having the rack on the roof? I removed my seldom-used roof bike rack and fairing hoping to improve fuel efficiency and didn't see a noticeable increase in mileage, though I wasn't tracking  15 Sep 2007 Does the fairing result in measurably better gas mileage? My best friend has Yakima racks on his Honda Ridgeline truck, and the noise from the un-faired roof rack was unbearable above 50 mph until he put a Yakima fairing on it, and then . When I used to do a lot of motorway miles, I noted the car did 1-2mpg less with the roofrack + bikeracks on top. The Rack Attack guys said sometimes with the roof rack,  Roof Box and fuel economy. What does this do to fuel economy? We broke this test into two parts: with empty roof rails (many of which are left up all year long) and then loaded with a cooler and  1 Mar 2007 Anyone run the numbers before and after? I'm interested in installing a typical yakima roof rack. A loaded roof rack can decrease your fuel economy by around. I am somewhat suspicious of  26 Apr 2016 While there have been studies of their impact on individual vehicles—depending on the configuration, the fuel consumption penalty can be 0 to 25 percent on passenger cars—this is the first study to estimate impacts at the national level. One person reported a 3 MPG drop from hauling a bike on the back of his car, but I'm interested in a roof rack, and how it might affect MPG while it's empty (no bike mounted). However, a loaded roof rack can decrease your fuel Listed below are some steps that will help reduce drag. No change in MPG noted with them alone. 7 May 2017 Does anyone have a comment or opinion re. 28 Sep 2014 Adding a roof box means your car has to carve a bigger hole in the air, which requires burning more fuel, so your mpg will suffer. I did have a set of Yakima load bars on the front for a while, and they were noisy. I am willing to take it out but I'm not sure how to remove it. The degree Hauling my SRQ17 on top of my Toyota Prius last June (with a Yak rack), made my mileage drop from about 50mpg to about 36mpg. Does any one have any experiance of how much the fuel economy will reduce by?. Couldnt fit into any car parks with a height restriction or multi stories. . The more important question to ask yourself is "Do I really NEED a roof rack?". It estimates that roof racks can reduce fuel economy on vehicles by 0 to 25 percent depending on the racks' configuration and if  24 Dec 2017 What Car? True MPG. The racks  Another way to ask the question is, “Do GasPods Work? Many variables affect your car's fuel consumption and how much you might improve mpg with GasPods. Also, reduce drag by putting bulky items inside the vehicle or trunk instead of on a roof rack. (That would be a serious hit to the fuel economy) For reference, I  “Despite the use of lightweight materials and aerodynamic profiles, a roof rack still adds a degree of weight and aerodynamic drag to your car. 3mpg – Roof bars and laden roofbox 30. So really it will pay for itself (eventually). 30 Aug 2012 Don't be fooled by the notion that a fairing will make your rack more aerodynamic and, therefore, improve your gas mileage. so here's my question for anyone who has one. Bikes don't Of course the Scion was never really designed with Aerodynamics in mind so my guess is that a roof rack can't hurt that much. Reply Reply Cargo of any kind on the roof of a vehicle will impact gas mileage. The car is a BMW 325 coupe, so the box is longer than the roof. (this on the theory aerodynamics . 5x tomorrow. If you are lucky enough to be driving a convertible in the summer, stop and put the roof up (provided its safe to do so) before you drive on motorways or fast A roads. 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  4 Jul 2013 As we cruised at 65 mph in the Accord with a pair of bicycles on a roof rack plus wind deflector, our highway fuel economy plummeted by more than a third, from a miserly 42 mpg to a miserable 27 mpg. Lose the Roof Rack. Wind drag is a  16 Jul 2015 This blog post looks at some way how you can reduce your fuel consumption and increase your mpg - bringing down the overall cost of your motoring! the fact that extra wind resistance = lower economy – therefore any extra bits on your car – like a roof rack, or a bike rack – can lower your fuel efficiency… 18 May 2006 According to an old HCH1 review, a roof bike rack will reduce your mpg by 1 or 2. 7mpg  Does My Roof Rack Affect My Gas Mileage? We know that aerodynamics matters a lot at highway speeds (the more 'slippery' your vehicle is through the air, the less your engine has to work to keep the vehicle moving), but what kind of impact does a roof rack have on MPG? Using a 2013 Honda Accord and data provided by Consumer Reports, an empty roof rack will increase the amount you spend on gas by 12% compared to no rack at all, assuming highway speeds. Vehicle with roof rack. • Reduce drag by placing items inside the car or trunk rather than on roof racks. A two-bike rack with wind deflector will increase your gasoline costs by 36%. But I know it did. 5mpg – Astra's baseline fuel economy 30. So saying a roof rack is expensive and costs you MPG does not mean you are paying for the *effects* of using so much gasoline. So yes take  I changed to larger tyres, fitted the roof rack, and had the injector pump overhauled at the same time so I don't know if any on e thing has caused a change in fuel economy. The rack alone wasted 5 mpg. “A national . Fuel economy benefit: 1-2%/100 lbs percent. Not surprisingly, when you add stuff  1 Jun 2016 You could argue that having a roof rack on your car makes it easier to stay fit: Throw a bike or skis on top, head over to the park or slopes, and burn off some calories on the trails. 16 Jan 2014 I have a 2013 Crosstrek Premium manual 5-speed. Even roof racks can decrease to your car's aerodynamic efficiency. I am talking about driving with the rack empty. I am of to the Alps in December and may need a roof box on the car. If the wind noise from your roof rack is bothersome,  26 Apr 2016 The roof racks that Americans use to lug skis and canoes and bikes in less-than-aerodynamic fashions are, it turns out, a serious drag on individual gas mileage. 8 Apr 2009 So, I added a Thule roof rack to my new (jan 09) CRV within weeks of buying it. So if you're not using it, take it off! “Finally, if you're planning on taking a trip to the safari park with a roof box  22 Sep 2008 Has anyone tested a dual-crossbar roof rack (either Thule or Yakima) with a fairing in front of it to see how mileage is affected? I'm sure noise will decrease, but its only worth the $70 or so investment to me if I stand to gain on mileage. 98% of the knuckleheads here can't compute MPG alone properly so to have someone here to accurate before and after testing will never happen. Increasing A loaded roof rack can decrease your fuel economy by 5 percent. My question is whether anyone has actually kept track of how much an empty roof rack would affect MPG on a daily basis? I've got a Yakima Load Warrior and with my mostly urban driving with a bit of highway I got about a half mile better MPG w/o it and I also did a test of it on nearly all highway last year  When I first bought my Thule Rack, I noticed immediately that I lost on average about 3 to 4 MPG. But, what most people want to know is how much fuel will they need for the driving they plan on doing, and how much a different car, a bike rack, etc. 2mpg – Two front windows totally open 29. The cumulative losses are for the first time being measured on a national scale; on passenger vehicles it could reduce  2 Oct 2009 This disruption would not cause as much of a mpg drop as a bike on the roof, but it does decrease your gas mileage. The addition of the fairing dropped this to about a 2 MPG loss, however, with current gas prices, and the amount of driving I have to do, I have leave the rack off unless I plan to use it. It slaughtered my mpg from around 50mpg down to around 33-36mpg travelling at 70mph or  Read more Gas Pains coverage: Destination: 35 MPG. thule fairing image via mtbr  For every 100 pounds of weight in your vehicle, fuel economy decreases by one to two percent. Has anyone taken those off and found any mpg benefit? I'd guess. Adding any rooftop carrier, cargo box, or ski rack doesn't come free. Other options a trailer? Does anybody know how having a bike on the roof will impact fuel consumption at motorway speeds? I. You mean the fairing? interesting as that is supposed to reduce wind noise and fuel consumption (for most cars)  28 Apr 2016 Most factory roof racks are carefully streamlined due to fuel economy worries — hell, some are downright sensuous — but the trouble comes from chunky, do-it-yourself . As far as fuel consumption, when you show me the alternative that does not adversely affect fuel consumption, I will take it seriously. You go and add other things to the silhouette of it, it will affect the mpg's. You will probably get the best gas mileage with the racks that attach to the back of your vehicle. 11 Dec 2008 im planing on making a roof rack but im wondering how much it will affect my millage. So you want your car to be as aerodynamic as possible for highway driving. You will find ZERO concrete evidence as to the affect of any accessory and MPG. But in all seriousness, it is worth exploring, because no one wants to be filling up their gas tanks more than necessary. In the long run, your $50 fairing is likely to cost you many hundreds of dollars in lost gas mileage. 18 Jul 2008 I'm want to know how much the roof rack affects my FE. If it's just for looks, I wouldn't waste the money. The distance between the roof and the bottom of the panel would be about 2 to 3 inches. But Thule aerobars minimise this  OEM rack for the R56 is the best you can get hands down because you can take it on and off and it is not that hard do it. S. Keep track of your fuel economy  i believe him, especially if its a lower horse powered vehicle. The question is do I remove the fairing, or leave it on? It seems like the fairing would block air from flowing under the box, and maybe cost a few mpg. The math just doesn't add up. Place items inside the vehicle whenever possible. I am not an engineer and can't explain why that happened, I have no idea. I'm most interested in gains at interstate highway speeds, at times when  Fuel economy science project: investigate how increasing air resistance by adding a roof rack to a car can affect fuel economy. I have been keeping track of my MPG using. Does anyone have actual numbers to report? When you installed your roof rack did you notice  Does anybody have any figures that would indicate the impact on fuel consumption that carrying a kayak on the roof of a vehicle has? I was told several With two adults and two boats on the roofrack (with cockpit covers) I get 26. In fact, it significantly cuts your highway mileage all the time it's installed, whether there's weight up there or not. I have gotten into the habit of carrying my bikes on the back of the car in the hitch mounted rack on longer distance drives. You know that Thule roof rack you keep on your car to convince people that you're really outdoorsy? 20 Mar 2011 For those using trunk racks, how much of a mpg hit do you take when carrying bikes? With gas prices continuing to go up, I'm looking at trunk racks to replace or supplement the roof rack. 26 Oct 2008 However, if everyone in the country did it, it would make a impact in terms of protecting the environment. I've seen a slight decrease  Anyway I digress, back to the original question, I will definately have a reduction in fuel economy with a roof cage ! Does anyone have an opinion on the different styles of Roof storage devices, My preference may be toward the Rhino cargo tray that attaches to standard roof bars, There are plenty of these  However, I couldn't find any numbers. A roof rack or carrier provides additional cargo space and may allow you to buy a smaller car. the rack seems to reduce MPG by like 8mpg on my prius adding two bikes Gas mileage is down a little with the rack on all summer, but more like 1-2 mpg, not 8. 51/gallon. It's also a surefire way to increase aerodynamic drag in a big way, which saps your efficiency at highway speeds. • Clear out your car; extra weight decreases gas mileage. didnt need all the stuff with the premium, but kinda am thinking about adding an aftermarket roof rack. Use Cruise Control. It's impossible to give an exact figure because it depends on so many factors, but Britain's biggest roof-box manufacturer, Thule, states that your mpg is unlikely to decrease by  Depending on design and whether you have a deflector on the front, these have been shown to reduce gas mileage by 10–15% even without anything on them. will affect how much fuel they need to buy. 17% was reported by a long distance commuter driving a Prius C. 13 Jun 2016 Take off the roof rack. I have a Yakima rack: Railgrab towers and round bars. Keep track of your fuel economy. Looks like Thule and Yamika have sets that fit the car. 5 May 2009 Buick Enclave: During the summer, when families are on vacation, it's a common sight to see SUVs with roof racks loaded with luggage. Removing common unnecessary accessories such as roof racks, brush guards, wind deflectors (or "spoilers", when designed for downforce and not  6 Nov 2015 Driving with tyres underinflated by just 15psi can mean a loss of fuel economy of about 6%. | Newser. Tests are conducted in a laboratory to ensure repeatability within 1%, but they are based on a real-world route that takes in town, rural and motorway driving. 28 Apr 2016 The reasoning is simple -- aerodynamics. He switched to a hitch rack. Declutter your car and think about items you don't need for every single trip such as prams, kids' scooters and beach gear. But, when I put a roof-top-tent on them (they are in the front of the van, fore of the roof rack), I lost almost 2 MPG (although  8 Apr 2014 What kind of gas mileage difference did you experience with your vehicle and a trunk mounted bike rack? (Details on both would be nice) I've been trying to find this info online, but most people seem to choose roof racks and I don't want that. In a documented test, Consumer Reports found that a 2013 Honda Accord with no rack got 42 mpg U. Disrupting airflow over the roof and causing turbulence has more of an effect the faster you dr Last year on a run to Paignton (900 round trip) we got about 35mpg fully loaded, roof box included. 15 Mar 2008 only when necessary. Moreover, use of roof racks is projected to increase given national  29 Jan 2018 In fact I notice no decrease in MPG even with the bike on top. It's aerodynamic. First, and  23 Feb 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% 10 Jul 2013 “I don't really notice it, just have to watch real careful in your mirrors, you know,” Wendell said. They used a Buick Enclave CX for the roof rails test but I think the results would be similar for the Escape. 25–$0. Ask The Experts a Question >>  6 Jul 2011 86-95 Trucks & 4Runners - Roof racks make a difference in MPG! On my way there, with my Yakima roof-bars and wind fairing on, me, clothes, tools and a few other things that are always in my truck, I got 20 MPG doing 60MPH in . ” In fact, they say the simple act of putting a rack on your ride can (depending on how it's attached) cost you up to 25 percent more in fuel consumption. the impact of fitting roof rails on economy and wind noise? nb. The impact of a rack depends on its configuration, and your driving speed. A large, blunt roof-top cargo box, for example, can reduce fuel economy by around 2% to 8% in city driving, 6% to 17% on the highway, and 10% to 25% at Interstate speeds (65 mph to 75 mph). I have never I would guess that the roof racks really kill gas mileage. 28 Apr 2016 The Berkeley Lab says its study was the first to extensively look at the national impact of automotive roof racks, which often hurt fuel economy due to additional aerodynamic drag. And quickly realized the wind noise would drive me crazy, so I dug up. With a bike in the rack, maybe 1 mpg less. You could also Green News Summaries. Does anyone know if adding a rack will decrease the fuel efficiency? thanks. And don't rag . The (not very rigorous) test: "A-B-C" I did these roof rack runs as part of the warm-up for last year's  16 Sep 2007 I purchased the feet and fittings, I already had the 50" bars from my old car which is the size thule recommends for this car. Hauling cargo on your roof increases aerodynamic drag (wind resistance) and lowers fuel economy. i was thinkin of throwin a thule box on my 03 subaru legacy sedan this winter. What to do instead: Unless you're hell-bent on maintaining  If you're like most Americans, and drive about 20,000 miles a year, increasing your car's fuel efficiency by 10 MPG can save you over a thousand bucks a year - not to mention countless stops at the gas station where you . Here's mine  Fuel Economy Benefit: 7–14%. 2mpg with 4 adults and 4 boats/gear for ten days on a trailerI get 25. Equivalent gasoline savings:. 5. Simple car modifications, such as ditching the roof racks and adding a vacuum gauge, can improve fuel efficiency, and are easy enough that even . About how much will it reduce fuel efficiency? I've heard that light haulers that attach to your trailer hitch are the most fuel efficient because  Indeed, roof racks at their worst can give an economy hatchback the fuel economy of a crossover SUV. Do these have just as drastic effect on fuel economy as roof mounted? I know aerodynamics are as important at the  Infrequently used items in your boot and on the backseat could be adding unnecessary weight to your car, increasing your fuel spend. The Thule Interstate Cargo Bag # TH869 that you referenced would be a great choice for a cargo bag and is confirmed to fit on the factory roof rack of your vehicle. You'll have less wind resistance than with a roof rack. I know there will be an effect when loaded so I am not interested in that. I would presume that boot mounted is better and that carried internally would be best (but your family may not be able to fit in the car). With a bike in the rack, it's a 5 or 6 mpg hit. 27 Apr 2016 Researchers say roof racks are “responsible for almost 1 percent of national fuel consumption. I had no noise increase with the rack. The worst item for mpg are bikes traveling on the highway. 0DTi Vecra estate. ” Results at a glance 30. So I decided to do a quick experiment to see what I could learn. Jameson C. There was actually next to no action taken to reduce oil market speculation. How much reduction in MPG should I expect with just the feet and bars alone? Is there a maximum weight capacity for what the Fit can handle on roof? (putting a canoe up there from  From my experience, the roof rack it self does not reduce mpg much at all, but when you start putting items on the rack is when the mpg really goes down. 25 Apr 2016 While there have been studies of their impact on individual vehicles—depending on the configuration, the fuel consumption penalty can be 0 to 25 percent on passenger cars—this is the first study to estimate impacts at the national level. Electric cars  14 Feb 2017 Furthermore, car maintenance factors like the condition of your tyres and brake pads can affect the safety, overall performance and fuel economy of fuel economy is also dependent on a number of different factors such as tyre pressure, excess weight in the boot, presence of roof racks, driving style, etc  29 Jun 2011 I can't give you numbers, but bikes on roof racks kill your MPG. How significantly will roof racks - with bikes - increase fuel consumption? The mpg decrease sounds like a lot, but they're still getting 35-40 mpgs, which is better than most vehicles without bike racks. The thing that's going to affect your MPG is going to be the size and shape of your cargo. Leaving a roof box or bike  Due to the need to carry 4 bikes now, roof mounted is no longer an option as we need the roofbox when camping so I am looking at getting a towbar mounted carrier such as Mottez or similar. Thanks. And they're becoming common enough to represent a drag on the fuel economy of the United States as a whole, scientists have found. That was a 2. At normal  Looking for anybody's experience/numbers on this. A large, blunt, roof-top cargo box can reduce fuel economy by 6% to 17% at 55 mph and 10% to 25% at interstate speeds (65-75 mph) and roof racks can diminish fuel economy by 10-25% when at highway speeds. The use of a profiled roof-box may enhance the aerodynamic properties of the tow-car/caravan combination and reduce fuel consumption. We use a roof rack/box or a bike carrier, but remove them when we get to our destination or after each use. 13 Oct 2016 Likewise, roof racks might look cool, but may not be worth thinning your wallet. The biggest problem we had was parking. Appearance: These days, looks are everything and a fairing can make that new roof rack look a lot sleeker