# Roof Mounted Rack MPG



## Santa Clauz (May 20, 2005)

Hello,
I will soon need to figure out a way to haul around my two bikes on my 2006 Civic SI. I think I would like to go the route of the Hidden Hitch but I worry as I have an aftermarket exhaust and im not sure of clearance issues. 
I know I have seen a pic or two on here of New SI's with roof mounted racks and I was wondering what kind of MPG hit they took with having them mounted. Also what help does the wind deflector you mount on the front have on mpg as I would prob buy one if it seemed like it helped a bit.


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## A1an (Jun 3, 2007)

I've daily driven two cars with roof mounted racks (an older Focus and a new Rabbit). Neither car saw any significant MPG loss with the rack and two carriers. The fairing does help quite a bit with wind noise, but again I didn't see any real MPG difference running the rack with or without the fairing. Hope that helps.


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## longman (May 9, 2007)

a hitch rack on a small car probably has a similar hit to mpg as a roof rack as the bikes are sideways to the wind and are still pretty much in airflow behind the car. The fairing is simply to cut down on wind noise and has varying affects on different cars depending on the position in relation to the windshield..in much the same way as the roof rack.


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## pimpbot (Dec 31, 2003)

*in my experience....*



longman said:


> a hitch rack on a small car probably has a similar hit to mpg as a roof rack as the bikes are sideways to the wind and are still pretty much in airflow behind the car. The fairing is simply to cut down on wind noise and has varying affects on different cars depending on the position in relation to the windshield..in much the same way as the roof rack.


'96 GTI 2.0l 4cyl

At freeway speeds, near sea level, which is 90% of my driving...

32-33 MPG with no racks
32 MPG with hitch rack and bikes, no change I can calculate
28 MPG with factory roof racks and two Thule lockjaw trays, no fairing, sunroof not usable
26 MPG with roof racks and two bikes on trays, sunroof not usable

So yeah, there is a significant hit, even empty. I also have been riding my Monocog 29er, which sticks out sideways a bit more than my 26er bikes


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## LCW (May 5, 2008)

i only recently got a Yakima roof rack for my 1.8T Jetta - and have only used it once for some significant highway time... but i'm thinking i'm noticing a bit of a hit... may 5-10% - which i guess is significant (but that's only from a sample size of 1, and I hit a couple of traffic jams lately which might be the bigger cause) - but i'll wait to do more miles and get more "data" to really make a proper assessment as to how much a hit it's making...

i'm getting a deflector (thought I could get awaw without one - but the wind noise/whistling is just too much... hope it also reduces drag a tiny bit...

peace


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## 245044 (Jun 8, 2004)

longman said:


> a hitch rack on a small car probably has a similar hit to mpg as a roof rack as the bikes are sideways to the wind and are still pretty much in airflow behind the car. The fairing is simply to cut down on wind noise and has varying affects on different cars depending on the position in relation to the windshield..in much the same way as the roof rack.


Sorry, but it's not even close. It cost me several MPG's with bikes on the roof. With my Subaru, bikes on the back have no effect at all on the MPG's.


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## Rev Bubba (Jan 16, 2004)

*10% to 12% reduction*

I find about a 10% to 12% reduction in mpg with roof racks. Probably around 15% with bikes loaded. I do note that road bikes reduce the mpg much less than mountain bikes because of their more streamlined shape and lower frontal area.

This % reduction has been fairly constant with a VW Passat, Subaru Legacy Outback Wagon, Mini Cooper and VW Golf/Rabbit.

Much has to do with how fast you drive. The slower you go, the less of a factor wind resistance will be.


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## horseonthefly (Mar 19, 2007)

With a mustang and 2 or 3 bikes on the roof I lose about 1-2 mpg city and 4-5 on interstates (I had been getting about 25 city and close to 30 highway, 3.8L v-6 5 spd). Basically the aerodynamic loss eliminated the difference in mileage between city driving and highway. The one major advantage to the hitch rack I've seen is in the handling department. Especially with small/light cars and big/heavy bikes you add a lot of weight (100+lbs for 3 bikes) with a very high center of gravity. Therefore, I've got tons of body roll in corners. Also, you will tend to get tossed around a lot on interstates. Whenever I get behind an 18-wheeler I can feel the turbulence tossing the car around in the lane. High cross wind will also throw you around a lot. All of these are tolerable but I thought I would warn ya so you don't do like me and go wtf when the bikes start swinging back and forth behind a big rig.


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## TurboasT4 (Oct 2, 2004)

*Absolutely noticable*

2005 Sentra SPEC-V:

On a 7 hour drive from Philly to Buffalo ---

34 MPG highway, no rack, no bikes, A/C off

28 MPG highway, rack, no bikes A/C on

25 MPG highway, rack, 3 bikes on roof, 2 passengers, no A/C

BTW, my car has a computer built-in that monitors MPG, average speed, etc. I also use the Thule Fairing which allows me to use my sunroof still.


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## kristian (Jan 20, 2004)

The only impact a roof rack has on your fuel economy is the increased wind resistance, so the effect is going to be directly related to the speed you drive. 

I put a roof rack on my '06 Civic this year which I didn't use last year. I track my mileage religiously (it's a hybrid) and I have not seen ANY impact to city driving mpg (speeds up to 50mph) with an empty rack. I pull the rack off whenever I go on the highway without bikes so I don't know what impact there is--I would guess a percent or two at least. If you have a 4 door Civic, it takes about 5 minutes to pull/put on the rack, but it might be more involved if your Si is a coupe.

It's hard to quantify the mpg impact of driving in the city with a bike on because of temperature fluctuations, trip durations, etc. I would guess I lose around 5mpg (about a percentage point less than my 55mpg summer average) with a bike on when driving city speeds. I haven't done much highway driving with the bike on but I think a 3-5% reduction in mileage would be a fair estimate--more than 3-5% if you're driving faster than 70mph.


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## Jayem (Jul 16, 2005)

pimpbot said:


> '96 GTI 2.0l 4cyl
> 
> At freeway speeds, near sea level, which is 90% of my driving...
> 
> ...


Yep, knowing what I know about aerodynamics, it's going to be noticable, but there are ways that it could be less noticable, like if you only get 17mpg to start with, you aren't going to necessarily see a huge hit, but your milege sucks to start with, or if you never get to highway speeds where the drag rising as a square of velocity becomes an inssue. Otherwise, it's almost always going to be noticable, because "good milege" comes mostly from good aeroydnamics and light weight, there are other factors, but those are two of the most important ones.


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## Jayem (Jul 16, 2005)

kristian said:


> I put a roof rack on my '06 Civic this year which I didn't use last year. I track my mileage religiously (it's a hybrid) and I have not seen ANY impact to city driving mpg (speeds up to 50mph) with an empty rack. I pull the rack off whenever I go on the highway without bikes


And that is one way to do it, because less than 50mph you aren't really going to see the drag effects much, but go above 50mph on the highway, and you most definitely would (again, it's aerodynamics and that's one of the most important aspects for "efficiency" with a car).

In any case, that $$$ adds up and easily covers the cost of a hitch and hitch rack after a while.

If anyone wants to see, just use the numbers that people are putting out here, calculate your estimated miles per year with and without the top rack, also include bike-trips of course with even reduced milege, then see how much it adds up to...it's pretty significant and the hitch rack pays for itself essentially.


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## Jim165 (May 6, 2008)

2001 Accord V6 Coupe with a Yakima roof rack + fairing and I'm averaging about 23 mpg without the rack and about 21.5 with. Mileage with the rack loaded with my bike isn't that much lower as I tend to drive the speed limit out of caution. This car's not exactly efficient considering it's size...


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## kristian (Jan 20, 2004)

Jayem said:


> If anyone wants to see, just use the numbers that people are putting out here, calculate your estimated miles per year with and without the top rack, also include bike-trips of course with even reduced milege, then see how much it adds up to...


I think that is a fair way of calculating it except for the caveat that you would only count your highway miles, not your city miles (based on my experience). Assuming you do 2,000 highway miles per year in a 30mpg car that got a 10% hit with a bike on the roof, it would take 16 years to pay for a hitch rack (assuming $500 for the hitch + rack and $4.00/g gas). Bump that up to 10,000 highway miles and the math bumps down to 3.4 years. If the price of gas keeps going up, getting a hitch rack gets "cheaper"...

K (averaging 60mpg so far today WITH the bike on the roof)

Edit: My math assumes that the driver already has a roof rack and is considering buying a hitch. For someone who doesn't already have a roof rack, the payback would be a lot quicker.


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## Jayem (Jul 16, 2005)

kristian said:


> I think that is a fair way of calculating it except for the caveat that you would only count your highway miles, not your city miles (based on my experience). Assuming you do 2,000 highway miles per year in a 30mpg car that got a 10% hit with a bike on the roof, it would take 16 years to pay for a hitch rack (assuming $500 for the hitch + rack and $4.00/g gas). Bump that up to 10,000 highway miles and the math bumps down to 3.4 years. If the price of gas keeps going up, getting a hitch rack gets "cheaper"...
> 
> K (averaging 60mpg so far today WITH the bike on the roof)
> 
> Edit: My math assumes that the driver already has a roof rack and is considering buying a hitch. For someone who doesn't already have a roof rack, the payback would be a lot quicker.


The best number I came up with (assuming no roof-rack exists) was about a year to pay off, and the issue of highway miles is definitely valid here. You also can negate some of the impacts by removing your roof rack, as you do. That's what I do with my hitch rack when I'm not using it.


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## scottzg (Sep 27, 2006)

my roof racks hit me for about 10% per tank. I leave the bikes racks on the bars and take the assembly off when im not using it.


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## G-VegasMTBiker (Apr 15, 2006)

I recently switched from a trunk rack to a hitch rack. When Using the trunk rack with even just one bike on it could notice a significant increase in drag on the car; harder to maintain speed, longer to accelerate on the highway, etc. Now with the Hitch rack I notice no difference in overall performance with the car (2000 Honda Civic btw). In addition I get better visibility with the bikes being lower than they were with the trunk rack. I'd never go to a roof rack setup with any car, even a hit of just 5 mpg is too much for me the way gas prices are going. 

It is a good laugh to see the people drive around town with the Kayak roof racks all summer long, because you just know they're only using them twice all summer.


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## ibhim (Dec 4, 2007)

I hace a hitch rack on my Corolla and haven't noticed a drop in mileage when traveling with a bike. Never used a roof rack on the Corolla to compare.

Hidden hitch doesent make a receiver rack for the Si model of the Civic. Curt does. http://www.etrailer.com/hitch-2006_Honda_Civic.htm Perhaps should email Curt (preferable to the retailer) to see if will support your aftermarket exhaust. From the looks of the picture, looks like the hitch goes above the muffler (rather than below) next to the frame so probably won't be a problem as long as the muffler follows the same path.

Also, note the free shipping on orders over $150 - so add some components to take it over the $150. I initially didn't wire the Corolla - because you don't need it for a bike carrier. When a hurricaine was approaching I couldn't rent a truck for plywood as none were available. Quickly wired it and rented a trailer. Has come in handy several times with light towing loads - bulky items at Costco, avoiding delivery charges on appliance purchase, etc.


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## pimpbot (Dec 31, 2003)

*Heh....*



G-VegasMTBiker said:


> I recently switched from a trunk rack to a hitch rack. When Using the trunk rack with even just one bike on it could notice a significant increase in drag on the car; harder to maintain speed, longer to accelerate on the highway, etc. Now with the Hitch rack I notice no difference in overall performance with the car (2000 Honda Civic btw). In addition I get better visibility with the bikes being lower than they were with the trunk rack. I'd never go to a roof rack setup with any car, even a hit of just 5 mpg is too much for me the way gas prices are going.
> 
> It is a good laugh to see the people drive around town with the Kayak roof racks all summer long, because you just know they're only using them twice all summer.


I have a neighbor who drives a Toyota Sienna minivan with a monster torpedo pod on the roof racks. She's a single mom with twin 10 year olds. I wonder if she knows why her minivan only gets 13 MPG.


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## Freshfish (Nov 26, 2007)

I have a 97 Accord 2dr 4cyl w a roof rack. On the freeway i used to get 28mpg @ 80mph. Now I get 24.5 @65mph. I did not notice a change in my city mpg. Like others have said, get a hitch rack if your trail heads require a lot of highway driving to get to.


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## rckhopper87 (Jan 25, 2008)

I have tracked my MPG/mileage per tank since my car was new and log it every time. Kinda OCD-esque but I think it's interesting. Based on my numbers my mpg is completely unaffected by the addition of my hitch rack which is used almost every time I drive my car. 

Go hitch if possible.


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## Tony (Jan 20, 2004)

One more datapoint... on my Forester, a Yakima Spacecase (big, black coffin) has less effect, about 1 mpg, than a bike, minus 2-3 mpg, on the roof. The coffins are streamlined and they seem to have much less of an aerodynamic impact than a visual one.

As with most others experience, the hitch rack has so little effect as to be in the "noise" of normal variation.


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## whitey199 (Jan 1, 2008)

I get around the same in my outback h6 no matter what. It varies from 19 to 22. My heavy right foot has more of an impact on my mileage than my rack. I also drive slower when bikes are on the roof so that helps. I take my rack off if I know I will be on the highway too. It is a Thule 450, and takes about 90 seconds to put on or take off. I spend more time making sure I have every thing I need for the ride.


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## Frs1661 (Jun 9, 2008)

I haven't noticed a difference with or w/o the roof rack on my mazda3.


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## HitchSource.com (May 7, 2008)

One of our customers ran an experiment with his Prius and found a pretty big difference, too. We posted the story on our blog:

Hitch Bike Racks Save Gas


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## AussieRider (Dec 24, 2006)

With my Subaru Impreza (2002, 2L wagon) I probably loose about 10-12% with 2 bikes & upto 15% with 3 on the roof


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## mattsteve (Dec 28, 2004)

Ya, I lose 8-10% with my Jetta TDI. At least on the highway.....

Still, 42 is not bad. It was the same for me with a hitch mount vs a roof rack......


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## SoDakSooner (Nov 23, 2005)

2006 Corolla (20,000 hwy miles per year... 85 miles of commuting per day...I know, I know) gives me a lot of data though. The speeds below are the normal highway speeds I travel, not average trip speed(Corolla won't go that fast)

Yakima rack with 2 King Cobra Trays and fairing

36 to 37 mpg w/o rack at 65mph
34 mpg with rack, also at 65 mph (36 mpg at 55 mph)

I don't commute with the bike, but on longer trips:

31 mpg with one bike, at 70 mph
24 mpg with two bikes, average 75 mph (only one trip worth of data)


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## bergjm (Jan 12, 2004)

I have a 2001 Camry (V6), and before I had the Thule fork mount roof racks, I got 25 mpg on the highway. With the racks empty, I get 23 mpg. City mileage remained pretty much the same at about 16 to 17. I ride all year long so the racks are always on.

I have not tracked the mileage with bikes on top.


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## dnoyeb (Sep 23, 2007)

I drove from Detroit to Boyne Michigan with 3 bikes in the back on 1 fillup of my 2001 Forester. On the way back I put one of the bikes on the roof. I had to stop and get a fillup about 20 miles out. It definitely affected my MPG.

Probably though, the smaller your engine the more of an MPG hit you will take.


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## O3EP (Jul 11, 2007)

I wouldn't worry about it too much. I have a 2003 Civic Si with a roof rack and fairing. The engine is not stock. Before any modifications to the engine I would get 30 mpg with 70-80% highway driving. I added a tuned computer, larger fuel injectors, a supercharger at high boost, an intake, and and exhaust. That took me down to 25-26 mpg at 70-80% highway driving. I drove without a roof rack for 2 years and measured my fuel economy at each tank. In August 2007 I added a Yakima roof rack with the fairing which has not come off my car. At 70-80% highway i get 25 mpg; in all highway driving i still get close to 30 mpg with my bike on the roof. It's all about what speed you drive and how heavy your foot is on the pedal. If you only give 30% or less throttle and don't haul ass everywhere then you shouldn't notice any major impact to fuel economy. I wouldn't want to drive fast with a bike attached to the car anyway - if it comes off for any reason that would be big trouble. Having an Si makes it hard to keep off the throttle when you know how sweet the engine sounds, but your engine gets far better mpg than mine in its current state. I couldn't put a hitch on the car as the car is low enough for that to make me nervous.

The bottom line is: yes it will add drag, yes you will hear it even with the fairing sometimes, and yes it CAN affect your gas mileage. Keep your right foot in check and you won't notice much difference.


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## morkys (Jul 27, 2005)

I am considering a hitch mount, of course, I just bought a roof rack with sidearms. Anybody know if using the sidearm mounts are a less aerodynamic, and more fuel-gobbling way to go? 

I'll wait and research before swapping anything. The thing I like about the hitch is it's easy to remove from the car completely, leaving just the hitch. Even the hitch can be removed in some cases. I just have to see about a hitch for my 2001 Corolla VE. I don't even know if I can mount a hitch to it.


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## rocks'r'friends (Mar 30, 2007)

My Matrix takes a hit of about 1.5L/100km with two bikes on a roof rack. As noted above, I also have a roof box, which only hits me for about 0.5L/100km. Around town I put the bikes on the roof, when I hit the highway I put the bikes in the car and use the roof box for gear. Better mileage, more secure.


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## Kristatos (Oct 15, 2007)

I think it is generally accepted (except for those in denial) that racks and bikes on the roof will decrease economy. But to look at it in this narrow of a view misses the point to some degree. I get a few mpg less in my car with a rack and bikes, but I also use the rack to transport other stuff, like a space-case, skis and snowboards. Overall, this enables my family and I to take road-trips in an efficient mid-size sedan and still get mid-20s in mpg (not the high-20s I get with nothing on the roof) or 30+ in my wife's wagon w/rack. I don't have to up-size to an SUV and get MPG in the teens on my road-trips, and suffer that same crappy mpg driving around town.


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