# Racks and gas milage



## zombinate (Apr 27, 2009)

Ahoy, I looked but, didn't see a thread like this

Want to start a discussion on the real world effect of racks on gas mileage. Hopefully others have had some comparisons that they can share. Please add what you have seen even if it doesn't directly contribute to my example below.

I have a 2005 Pontiac Vibe (Toyota Matrix Clone), automatic, AWD. When I purchased it, there were square Thule bars already installed by the previous owner, and I added my Sidearms. MPG around 25MPG (without the bike), and 275-ish miles per tank. 

This last weekend I took off the whole set for a long weekend highway trip. It was used almost solely highway driving, but my MPG jumped to about 37MPG, and I was able to get 365+ miles on the tank. This week, I am back to my regular routine, so I will be testing what a road/hwy mix can do. With the MPG boost I have seen thus far, if it holds up with city driving, I am considering installing a hitch for a rear rack setup. I try to get out multiple times per week, so whatever I choose will likely stay installed.

Anyone have any experiences to share about the differences they have seen between roof and hitch mounts on the same vehicle? Or differences in what specific racks have (for example, I'd be curious if something lower profile has much difference; like sidearms vs 1up on the roof)


----------



## pop_martian (Mar 20, 2007)

I have a Prius I use for commuting. With no rack anywhere I get about 55 MPG. My roof rack drops it all the way to 43 with no bike and even lower with a bike. My hitch rack takes me to high 40s with no bike and mid 40s with a bike.


----------



## Shakester (Jun 26, 2012)

A roof rack does produce lots of wind drag. I took a trip with my SUV with 2 bikes mounted to Thule racks on the roof and drove 200 miles. I got 14-15 mpg. I then switched to a trunked mounted rack and that jumped up to 20 mpg which isn't bad for an SUV. Without any kind of rack, I usually get around 23 mpg.


----------



## JoePAz (May 7, 2012)

The best set-up for gas mileage is a hitch rack. Less impact with the bikes on it than roof rack and zero impact when you take rack off the hitch on the car. I never understand why anyone would drive around for any time with a hitch rack on the car, but no bike. I can understand if you on a trip, but back and forth to work? Come on the rack is connected by one bolt and east to remove and leaves the car or truck pretty much clean.


----------



## Timeless (Mar 23, 2007)

JoePAz said:


> The best set-up for gas mileage is a hitch rack. Less impact with the bikes on it than roof rack and zero impact when you take rack off the hitch on the car. I never understand why anyone would drive around for any time with a hitch rack on the car, but no bike. I can understand if you on a trip, but back and forth to work? Come on the rack is connected by one bolt and east to remove and leaves the car or truck pretty much clean.


Honestly the reason why my hitch rack stays on my car petty much 24/7 is I use it 3-4 days a week. It is more than just taking off 1 bolt. If I want to store it in my car I have to fold everything in and then set it in the car. Taking it inside all that work as well is carrying it up 3 flights of stairs.

The other part is the rack is heavy as it is about 45lb of and rather bulky.
So it is a mixture of those 2 things. I am using quite a bit and it is just really easy to drop the rack and lock up the bike instead of taking it off. That being said if I know I am going to be off the bike for a week I do take it off.

As for the orginal question. On my Sentra with a roof rack I had about a 1 mpg different wiht just the rack. It went from 28-29 mpg down to 27-28 mpg Hwy. If I put the bike up their it dropped another mpg. Mind you it had the larger engine so it had more over head to work with. 
My current car is a crosstour and I have a hitch on there. The difference is pretty much nil. I have MAYBE a .2 drop if I have a bike on their but in all honesty I been getting the same distance per tank as before I put on the hitch and same MPG.


----------



## Appalachian (Apr 12, 2006)

On my '06 Tribeca, I usually get about 22mpg on Hwy driving. This past weekend I put a rack and two bikes on the roof and got less than 18mpg.


----------



## JohnJ80 (Oct 10, 2008)

You can't compare the mpg effect of a rack from one car to another unless they both get the same mpg without the rack. 

J.


----------



## Barman1 (Jan 8, 2014)

My SX4 got 21.7 mpg without the roof rack and 21.4 with.
I haven't taken any long trips with the bike on the rack but I'm sure it'll drop a little.
The issue I have with a hitch mount is that it's a real pain mounting a hitch under an SX4 and honestly I'd be petrified with tailgaters. Even with a hatch mount there's a lot of damage that could be done with a light tap even.


----------



## Appalachian (Apr 12, 2006)

JohnJ80 said:


> You can't compare the mpg effect of a rack from one car to another unless they both get the same mpg without the rack.
> 
> J.


I think what we see here is that bikes on the roof can drop economy 20%+.


----------



## JohnJ80 (Oct 10, 2008)

Appalachian said:


> I think what we see here is that bikes on the roof can drop economy 20%+.


I would say that is misleading. It is fair to say that the more fuel efficient the car, the greater the percentage loss will be. However, in both cases, the cost in dollars to drive that those bikes down the road will be identical.

It takes a finite/fixed amount of energy to push a certain drag through the air at a given speed. You need to look at this as gallons per mile instead and the gallons per mile required by the rack is a fixed number.

As an example and for easy calculation, if you had a car that had gas mileage of 10mpg and you lost 1mpg with a rack, that would be 0.01 gallons per mile required by the rack drag because it would be 1/10th of the total gas per mile of 0.1 gallons per mile for the car to go one mile without the rack.

If you put the same rack/bikes on a car that got 20mpg then it would still require the same 0.01 gallons per mile to drag that rack through the air at highway speed.

Since the car by itself gets 20mpg and adding in the drag due to the rack/bikes for 0.06 gallons per mile (0.05 for car plus 0.01 for rack), the fuel economy of the car per mile would then be 0.06 gallons per mile (16.67mpg) or a loss of 3.33mpg at 20mpg. That's a 17% loss for the car with better mileage compared to the car with poor mileage of 10%. So as the gas mileage of the car increases, the resulting percentage loss is greater - but the financial cost is the same since it's the same 0.01 gallons of gas required to drag the bikes through the air at highway speeds.

J.


----------



## JL911 (Jun 17, 2014)

JoePAz said:


> I never understand why anyone would drive around for any time with a hitch rack on the car, but no bike. I can understand if you on a trip, but back and forth to work? Come on the rack is connected by one bolt and east to remove and leaves the car or truck pretty much clean.


I keep my hitch rack mounted to my jeep all the time. It has a locked and threaded hitch pin bolt that would be a real pain to take on & off several times per week.


----------



## bismirle (Dec 30, 2004)

I noticed my gas mileage dip when I put a Yakima roof rack on with round bars. It was crazy noisy too. I added the fairing and I my gas mileage went back up and the noise went away. It is an expensive slab of plastic but it does that job. That is without my bike up there. 

Once the bike is up top the mileage is shot for highway driving. Driving across Nebraska the car could barely stay in 5th at 75. Dropped down to 65 and the rpms settled to where they usually sit. Since I mostly stay within a couple hours from where I live it isn't too big a deal.


----------



## JL911 (Jun 17, 2014)

JohnJ80 said:


> I would say that is misleading. It is fair to say that the more fuel efficient the car, the greater the percentage loss will be. However, in both cases, the cost in dollars to drive that those bikes down the road will be identical.
> 
> It takes a finite/fixed amount of energy to push a certain drag through the air at a given speed. You need to look at this as gallons per mile instead and the gallons per mile required by the rack is a fixed number.
> 
> ...


----------



## Gritter (Dec 21, 2010)

bismirle said:


> I noticed my gas mileage dip when I put a Yakima roof rack on with round bars. It was crazy noisy too. I added the fairing and I my gas mileage went back up and the noise went away. It is an expensive slab of plastic but it does that job. That is without my bike up there.
> 
> Once the bike is up top the mileage is shot for highway driving. Driving across Nebraska the car could barely stay in 5th at 75. Dropped down to 65 and the rpms settled to where they usually sit. Since I mostly stay within a couple hours from where I live it isn't too big a deal.


I was wondering if a fairing would help mpg. Seems counter-intuitive, with larger surface area, but if you say so I believe you. I'm going to try it now.


----------



## pop_martian (Mar 20, 2007)

Gritter said:


> I was wondering if a fairing would help mpg. Seems counter-intuitive, with larger surface area, but if you say so I believe you. I'm going to try it now.


My gas mileage decreased with my fairing attached. Much quieter though.


----------



## euroford (Sep 10, 2006)

bikes and racks never made a noticeable difference for me, not on the Focus, the Escape, nor the F350.

i'm sure it made a difference... just not enough for me to give a crap.


----------



## jonz (Mar 23, 2009)

pop_martian said:


> My gas mileage decreased with my fairing attached. Much quieter though.


^This was my experience as well.

I switched to a hitch rack a few yrs ago for a number of reasons, but the primary reason was the MPG loss with roof rack (with and without bikes.) Granted I average about 35,000 miles/yr of almost entirely highway miles, so the $$$ adds up fast.
IIRC, I was taking about a 15-20% MPG hit without bikes on a '02 VW Golf, mostly highway, with a Thule rack and fairing


----------



## zombinate (Apr 27, 2009)

JohnJ80 said:


> I would say that is misleading. It is fair to say that the more fuel efficient the car, the greater the percentage loss will be. However, in both cases, the cost in dollars to drive that those bikes down the road will be identical.


While I think this is true, I think it is fair to say that roof racks tend not to be installed/uninstalled on a regular basis. Thus there is a convenience cost to keeping the rack installed as well.

If someone has a vehicle that is getting 35mpg average with a naked roof, and 25mpg with the rack on (slightly lower mpg yet with the bike attached). A 15k mile year then uses 429 gallons at 35mpg, and 600 gallons at 25. That 171 gallon difference at $3.50/gallon is just under $600. In my mind, that $600 is the convenience cost of not having to take the roof rack off when a bike isn't being carried.

I am happy paying the convenience cost of transporting my bike outside of my vehicle, but less excited about the cost of just having the rack installed. If a hitch, or other, solution has half the convenience cost, that ends up being hundreds of dollars a year I can save.


----------



## Flyin_W (Jun 17, 2007)

^ Much effort for a steaming pile of hypothetical bullshiite!

Honda Accord (4 cyl) 30 mpg. Add roof rack with fairing, 2 bike mounts, and kayak cradles 28 mpg. Add bike(s) 25 / 26 mpg.

Also know that being rear ended in a parking lot with bikes on a hitch rack costs much more.

(tapa)


----------



## gribble (Mar 1, 2007)

BMW 320 diesel wagon, auto gearbox.

Gas mileage is 47 mpg (but these are metric/euro gallons, smaller than proper US/imperial gallons). Car is very frugal though.

This is for a car with Thule Aero bars and pair of Thule Pro ride 591 (side arm) bike racks.

Convenient to have the racks on the roof, but wind noise is a pain. Turning up the stereo is the best option.


----------



## Tweakophyte (Sep 3, 2013)

I think you have to consider the HP and torque of the car, along with the Cd and the rack configuration. I've gone through two tanks of gas with my whispbars on my S4, and can't quite tell the impact because my routes have not been consistent. In fact, on the drive home the other night the car's trip MPG was higher than I've ever seen it.

While I'm sure the MPG is reduced, my car is not showing it right now.

PS Whispbars with nothing on it (as well as when I had the 1up roof rack on) remain pretty quiet.


----------



## bugshield (Jun 22, 2012)

JohnJ80 said:


> I would say that is misleading. It is fair to say that the more fuel efficient the car, the greater the percentage loss will be. However, in both cases, the cost in dollars to drive that those bikes down the road will be identical.
> 
> It takes a finite/fixed amount of energy to push a certain drag through the air at a given speed. You need to look at this as gallons per mile instead and the gallons per mile required by the rack is a fixed number.
> 
> ...


That may be true for the bike and rack themselves but I think that you have to account for screwing up the airflow over the car too.

I have extensive experience with roof racks on a couple cars and limited experience with a hitch rack. I was really disappointed on one trip with the hitch rack to have the same MPG penalty that I got with the roof rack. I was hoping for less! I don't know about an unloaded hitch rack as I would just take it off, but I can feel just the roof rack without bikes and took it off for long runs without bikes.

Our dearly departed Civic HX would get 45mpg @65, [email protected] or more, and 36mpg with bikes on @75. It would barely stay out of VTEC @65, hence the big penalty for going faster or adding bikes.

Our Civic SI really took a dive in MPG with the fairing on, so I didn't even think to try it on the HX. I don't remember the MPG figures.


----------



## bugshield (Jun 22, 2012)

PS. That's wheels on for the hitch rack, and fork mounted for the roof rack.


----------



## Flyin_W (Jun 17, 2007)

bugshield said:


> ...
> Our dearly departed Civic HX would get 45mpg @65, [email protected] or more, and 36mpg with bikes on @75. It would barely stay out of VTEC @65, hence the big penalty for going faster or adding bikes...


I had a '98 HX with the exact same results. But didn't learn as easily. With skis, no biggie, with bike & kayak - arrrrgh!

Not only did MPG take a big hit, but I had to became Fred fricking Flintstone on big hills!

(tapa)


----------



## cabarnett92 (Jun 21, 2014)

'07 Mazdaspeed6. 2.3L turbo, 6MT, AWD. Usually average around 25 MPG highway unloaded. With a trunk mounted bike rack (with bike), my average dips to around 23 or 23.5 MPG.


----------



## zombinate (Apr 27, 2009)

Flyin_W said:


> ^ Much effort for a steaming pile of hypothetical bullshiite!


Ah, the levelheadedness of the internet. Fair enough though, here are my actual results (general mix of 70%city 30%hwy):
2005 Pontiac Vibe 4cyl auto AWD
Just thule crossbars: 25mpg
Thule Sidearms added: 22mpg (without bike)
No roof rack: 29mpg

cost of having the sidearms installed for a 10k mile year (assuming $3/gal gas) = $331

Conclusion: Installing/Uninstalling rack much more frequently, or a Hitch rack, is in my future.


----------



## american henchman (Feb 13, 2014)

with my yak. rack. on my focus. i lost 7 miles to the gallon. 35 with out rack and 28 with cross bars, fairing, and steelhead mount. without fairing i lost 5 mpg


----------



## JohnJ80 (Oct 10, 2008)

Tweakophyte said:


> I think you have to consider the HP and torque of the car, along with the Cd and the rack configuration. I've gone through two tanks of gas with my whispbars on my S4, and can't quite tell the impact because my routes have not been consistent. In fact, on the drive home the other night the car's trip MPG was higher than I've ever seen it.
> 
> While I'm sure the MPG is reduced, my car is not showing it right now.
> 
> PS Whispbars with nothing on it (as well as when I had the 1up roof rack on) remain pretty quiet.


You know, for the whisbars, I also was pretty surprised. I have a 2006 530xi BMW wagon. I have the whispbars that go between the roof rails so they looked like the factory ones. I'd have to say that the car is quieter with the bars on than off when driving in the car. I also noticed no difference with the bars on or the bars off in average gas mileage. With the traditional square Thule bars, I lost around 1mpg max.

If you look at the bars from the front, they present very little cross sectional area. To them I have mounted the Thule Echelons that also are quite aero with little cross sectional area. With all of this, there was also no difference in gas mileage.

J.


----------



## mtnbikej (Sep 6, 2001)

JohnJ80 said:


> I would say that is misleading. It is fair to say that the more fuel efficient the car, the greater the percentage loss will be. However, in both cases, the cost in dollars to drive that those bikes down the road will be identical.
> 
> It takes a finite/fixed amount of energy to push a certain drag through the air at a given speed. You need to look at this as gallons per mile instead and the gallons per mile required by the rack is a fixed number.
> 
> ...


----------



## grizzler (Mar 30, 2009)

My 2009 matrix s gets 28-29mpg highway with no rack. 24-26mpg highway with roof rack with 3 bikes.


----------



## DennisF (Nov 4, 2011)

Speed is a big factor. Air drag increases by the square of the speed. Double the speed, quadruple the drag. Increasing speed from 50 to 70 about doubles the drag. Slowing down a little can make a significant difference in fuel burn.


----------



## GSJ1973 (May 8, 2011)

LOL. I love seeing roof rack mounted ski racks on cars in July. 

Talk about throwing money out the window, literally.


----------



## JohnJ80 (Oct 10, 2008)

GSJ1973 said:


> LOL. I love seeing roof rack mounted ski racks on cars in July.
> 
> Talk about throwing money out the window, literally.


All depends on where you live and what you do.

Arapahoe Basin Ski & Snowboard Area | Summer Ski Season

J.


----------



## edubfromktown (Sep 7, 2010)

With two bikes on my hitch rack I typically lose around 4 MPG on the highway (~24-25ish vs 28-29 MPG) in my 2010 Honda. I generally drive it like I stole it :thumbsup:


----------



## phsycle (Apr 14, 2011)

I would say about 10% loss across the board (with the roof rack only). With bikes up top,.....dismal. Hitch mounted racks + bikes took about a 10% hit in our Subaru.


----------



## JohnJ80 (Oct 10, 2008)

Hitch mounted rack caused a loss in gas mileage?

J.


----------



## phsycle (Apr 14, 2011)

JohnJ80 said:


> Hitch mounted rack caused a loss in gas mileage?
> 
> J.


Yes. Any surface area causing wind resistence to increase will affect the MPG. Even though the rack is right behind the vehicle, there is still wind resistence, especially since most cars have a tapering tail section. As I noted, 10% hit includes bikes being on the rack as well.


----------



## JohnJ80 (Oct 10, 2008)

phsycle said:


> Yes. Any surface area causing wind resistence to increase will affect the MPG. Even though the rack is right behind the vehicle, there is still wind resistence, especially since most cars have a tapering tail section. As I noted, 10% hit includes bikes being on the rack as well.


Your bikes protrude out to the sides - is that what you are saying? We see no change in gas mileage with bikes on the back but that's an SUV and there is very little protrusion to the sides.

J.


----------



## phsycle (Apr 14, 2011)

JohnJ80 said:


> Your bikes protrude out to the sides - is that what you are saying? We see no change in gas mileage with bikes on the back but that's an SUV and there is very little protrusion to the sides.
> 
> J.


In my experience, it doesn't matter that much. I had my 29er back there, which one of the wheels stuck out a few inches past the body line. So the next time, I took off that wheel so there was no protrusion. Not much difference in MPG (not enough to be significant when taking into account all of the other variables, anyway).

My car is a 4-cyl Subaru. Perhaps the bigger engine and the larger/more square and flat back side may reduce the wind resistence and thereby not affect the MPG as much. I don't know. This has been the case for any number of cars I owned. But now that you mention it, the big SUV I owned a few years ago may not have had much loss in MPG, if I remember right.


----------



## TiGeo (Jul 31, 2008)

2013 Ford Focus HB. Yakima roof racks, standard feet/round bars, 2 bike carries (fork mount), fairing. I estimate it knocks 2-4 mpg off of highway mileage.


----------



## patineto (Oct 28, 2005)

We have this set up on our Outback and I can see a drop of about 5MPG on freeways rides in the city I have never bother to measure, plus the wind drag and noise are noticeable, the problem is that we take the doggies to the park pretty much every afternoon so we only use the hitch rack on long trips with out the doggies (also a pain to get bags in and out)


----------



## ou2mame (Apr 23, 2010)

I lose about 4 or mpg with my Thule rack. Used to be more when my fairing got stolen. It's way too much work to take on and off every other day, and I don't drive the car too much so whatever. 

Sent from my 831C using Tapatalk


----------



## aKore (Jun 29, 2006)

I have an 08 Impreza OBS (4eat), with the OEM rack, an Inno Fairing, and two TieRod fork-mount bike racks.

Just finished a 2000-mile road trip to Colorado with two bikes on the roof and got an average of 23.4mpg. Without bikes I get 28-30 at 55-60mph, and 27-28 at 70. Many of the roads in Wyoming, SD, and Nebraska were 75 or 80, hilly and really freaking windy, so that's where I took the hit. I'm fine with it though, because the time savings were worth the drop in mpg.
I will say that I get better mpg and almost no road noise with the bike racks on as it breaks 'the stream'. Without the bike racks the mass of air would pummel the roof whereas now it just glides over it.

Added pic of my best mpg, as well as the car.
Can anyone recommend bug shields for the bikes? 
The mass of bug guts was very unpleasant.














Edit: Just realized I haven't posted for five years and have been a member for 8. Where does time go...


----------



## phsycle (Apr 14, 2011)

aKore - If I used my roof rack regularly, I would get a bike bra.

Skinz Bike Protection at Racks For Cars - www.racksforcars.com


----------



## tuffguy (Feb 13, 2010)

I'm still in the middle of a cross country road trip with my 2002 Volvo V40 with a Kuat NV rack on the back carrying two bikes. my "normal" hwy mpg without the bikes was always around 28-30. When crossing through Oklahoma/North Texas my mileage dropped below 24, and went up to 28 as I headed north/northwest from Moab up to Portland, OR. Though most of that, we were going through a gnarly headwind. in the first 300 miles of my return trip, I'm getting over 34 mpg (new record with or without bikes!) The real test will be the New Mexico-->Arkansas leg which was the worst I've ever had.


----------



## kapusta (Jan 17, 2004)

I have always been a mileage nerd. I calculate it nearly every tank. My 2003 CR-V gets 24-25 mpg. Does not seem to change much highway (typically drive around 75 mph) or in-town driving.

Putting an empty roof rack on it makes no measurable difference. Surprisingly, a very large Thule box also has no measurable impact. Might lean more toward 24 than 25, but really negligible. 

What DID make a huge difference is when I put on a fairing to stop the rack noise when nothing was attached to it. Knocked the mileage down to around 21-22 at highway speeds (with or without the Thule box). I realized that the Thule box itself stops the noise, so for a couple years I just left the thule box on there. Got 24-25mpg the whole time.

On a recent trip, my Thule box was showing signs of cracking, so I borrowed another box that is about the same size. KILLED my mileage when I got going over 60 mph, dropped to 18-19 mpg when doing 75-80. Below 60 I was back to around 24-25mpg.

I guess it all depends on the particulars of the car and whatever you have on top of it. Rack has no effect on mine. The particular Thule box I have makes no difference. Different box same size.... big difference. 

Bikes on the rear spare tire rack also have zero mileage impact on my mileage.


----------



## bradkay (Apr 9, 2013)

Like Kapusta, I tend to calculate my mileage every tank. I drive a '91 Loyale wagon and get @28mpg around town and @30mpg with highway driving. I have found no difference whether I have up to two bikes on the roof, but if I have 3-5 bikes on the roof I lose about 2mpg. Since my car is an old Loyale, I don't do much 70+ mph driving (90hp when new, a little less at 325,000 miles). Admittedly, I have never driven the car without the roof rack at all - my bikes are too important to me to risk them any other way. I do not use a fairing - never have. I first started using Yakima roof racks in the early 80's with my 1980 GL wagon and will never switch.


----------



## ImaBum (Jun 1, 2014)

I'm about to take my car on a road trip.. about 1500 miles round trip.

My car gets about 33 @ 71 mph. 22 in the city (I am fairly hard on the gas..it's a sporty lil sucker).

However loaded down with a 50# bike, small ice chest, duffle bag of clothes for a week and my 3 day pack.. I'll have an easy 150# in the trunk.

Curious to see how well I do. I'll be driving up the 101 highway (coastal highway) up to my destination and down I5 highway (interstate) on my return home.

..I've been tossing the idea of having a hitch installed but at the end of the day that'd cost $300 for the setup. Or a roof rack system also at least $300. For $150 more in fuel I can just drive my truck and save $150.

It's going to suck having to remove the front tire but it's the price we pay.

I would like to get a bike rack though for the truck as I just started getting back into biking!


----------



## Nomadllc (Nov 9, 2012)

Has anyone tried turning your handlebars sideways on extended trips? I think I'll try it tomorrow for the first half of our 1000 mile drive, then switch. 
08 Outback wagon 2.5l.
best milage is NEVER more than 26!


----------



## Tystevens (Nov 2, 2011)

Nomadllc said:


> 08 Outback wagon 2.5l.
> best milage is NEVER more than 26!


I had an '07 Subaru Outback. With bikes on the top and driving freeway speeds (70-80 here in Utah), my mpg was often in the 19-21 mpg range. Bikes on hitch rack would net 23-24 for a road trip. No bikes or rack, I would get 26-28 on the freeway.


----------



## VTSession (Aug 18, 2005)

Interesting to see these various figures. My '15 VW GTI, 6 speed manual claims 34 mpg highway but with no bikes and my 2 Thule sidearms I can easily get 34 mpg with all highway driving. Otherwise with bikes on the roof I get about 28 mpg combined. 

I am interested getting a faring but the Thule one seems a bit small and not too appealing. Any other fairing recs?


----------

