Hauling and gas mileage

I don’t often need to haul kayaks, since I keep mine at my bay house with its own dock, but Pamlico’s question got me thinking:

For hauling 2 kayaks, what would hurt your gas mileage more, cartopping them, or trailering?

My guess would be trailering would give you the worst gas mileage, but I am curious to know how it really works out form those who have tried both.

Seems to me
I have never car topped mine but i either put them in the back of my truck or ona trailer. It seems to me that i get worse gas milage when i am pulling the trailer. Thats not very scientific but thats just my experience.

Still haven’t …
completed the answer to this question. I’m sure a lot depends on what your vehicle is. I belive a big gas guzzler with lots of power will be affected less than a car designed for passenger use.

My observations to date:

Mitsu Montero sport, neckid- 20 mpg

With two on roof - 18 mpg

With two on roof, and two on trailer- 17 mpg

two on trailer, none on roof - ?

Don’t know yet, but I’ll bet it’s not significant with this vehicle, I’d guess about 18, but it’s only a quess for now.


depends on speed
If you are driving at highway speeds, where aerodynamics make more difference, boats on a roof should have more of an impact than on a trailer.

At slower speeds (like around town), the trailer would likely have more impact as it adds more weight that has to be accelerated.

I think Peter CA has it right
I cartopped two 13-foot kayaks on a Toyota Prius, loaded with camping gear for a week. We normally get about 55 mpg, but with the extra weight and the kayaks on the roof, our mileage was “only” about 45-47 mpg. We seemed to do better under 45 mph…at highway speeds the wind resistance’s effect was more notable on the mpg. I imagine the extra weight of a trailer would have the same general effect.


less then you think. I used my Saturn to go from North carolin a to New york, empty, no boat iwould get 27-30 mpg. up mountains etc driving with traffic (65-75 mph)Fully loaded, 4 adults( well technically I am an adult) camping gear, and an 18 1/2 foot Minn2 on the roof. milage was around 25. One time coming back from florida,just RedcrossRandy and me, all flat ground and driving slower then was my want I got over 30 mpg! The sticker said that highway was 29 Mpg…

Some kayak trailers are very light

– Last Updated: Jan-05-07 12:31 AM EST –

I once saw a trailer for carrying a pair of kayaks that was made of aluminum and had very lightweight wheels. An average person could easily pick it up, yet it was quite stiff and durable enough for the job. Even a small fishing-boat trailer, like you'd use for a 14- or 16-foot aluminum boat, only weighs about 180 to 200 pounds, and lightweight trailers like that really don't have much affect on performance (no different than carrying a passenger, and there is very little wind resistance). Since wind resistance increases exponentially with speed, I'd expect a trailer like that to provide better MPG on the highway since the boats are in the wind shadow of the car, but I don't have the personal experience to prove it.

Back when I used to carry a small jon boat on my Subaru, having the boat on top greatly reduced the amount that I needed to use the brakes, an indication that there was a lot of wind drag going on. Coasting down exit ramps with the throttle at idle, on ramps which were very familiar to me, I'd find that the car slowed down to a certain speed (roughly 20 mph) a few hundred feet sooner with the boat on top than without, but that boat was probably a bit less aerodynamically efficient than a pair of kayaks.

That sounds about right
My initial thought was highway speeds, because if I ever needed to transport (other than the half-mile to the beach side of Galveston) I would be doing highway speeds, but I guess that might not be true for most people.

My experience
with a Suby Outback 4 is:

A cruise-controlled jaunt up I-79 and across I-68 with a naked roof averages out almost exactly 27 mpg.

Add a touring boat and a cargo box or a solo canoe and the same trip mpg drops to 22. I-79 in WV is quite mountainous, and is a mpg-killer.

Interestingly, simply putting my Yakima crossbars on the roof will drop the mpg to about 24-25.


Toyota Camry
MPG on highway without rack or boat = 34.

MPG on highway with rack + one canoe = 25. This is a significant loss of fuel economy.

I wonder if a light weight, tear drop shell shrouded trailer would be more fuel efficient than roof racks. The big freight haulers have looked at this extensively. From the little I have read about it, the greatest drag occurs at the tail end of the trailers. But this obviously creates design problems for the rear loaded trailers.

If the crossbars do that,
then your vehicle is greatly affected by rooftopping, which is borne out by your example of I-79 (27 mpg with no boats on top, 22 with them). It’s not the mtns in that case; it’s the wind resistence.

I keep Yakima crossbars on my truck all year and it does not change mpg a whit. (Of course, in a completely controlled wind-tunnel test, it might have some effect.)

My husband’s Outback gets 28 mpg around town, which includes the extreme terrain changes to/from home. He is curious about what it would get on an all-highway jaunt but we never use it for that. I’m thinking it wouldn’t be much higher than the 28 mpg because it does not appear to have an overdrive gear and would be revving kind of high above 60 mph.

Car top, costs 10 miles a tankful

City or highway/speed (aerodynamics would seem to favor a trailer and stop and start favor cartopping)

Type, width and weight of trailer, tire width

type of vehicle

Have to admit the right trailer would appeal to me. Has to be savings in that eventual trip to the chiropractor.

If you keep you speed down I don’t
think either way the gas mileage will be about the same. With two canoes on my truck my mileage drops about two miles per gallon and while towing a small UHaul it was the same drop. When I tow my travel trailer, the mileage doesn’t change if I have the canoes or not on the truck. I found out that going too fast with the trailer is very hard on its tires so I keep my speed down and don’t have any more wear problems. If you keep your speed reasonable, your mileage shouldn’t suffer too much either way you carry your yaks.

Less “droppage” when windy, too
A friend dropped a kayak from his roof rack and took out a hunk of gelcoat. The wind BLEW it right out of his hands. I was extra-glad to have a trailer that day.

Can I make this generalization?
From reading the above posts, the drop in mileage will be proportionately greater from light, higher mileage vehicles (small to mid size sedans and SUVs) than from heavy, lower mileage vehicles (trucks and large SUVs).

Probably true
As Pikabike noted my loss of mpg is more due to wind resistance than mountainous terrrain. And if the HP/weight ratio of your vehicle is high your loss should be less than if you add a bunch of drag to a smaller econo car.

I get the (reasonably) good mileage I do, in spite of having AWD because I have a “sport shift” automatic. On the highway I shift into 4th where the tranny stays until I downshift for a hill.

Oh, just to stir the pot, I do notice a difference between hauling a touring kayak and hauling an open canoe. Canoes are noisy and drag teh mpg down more.


Subie Outback 4
with two sea kayaks on the roof (Thule rack) drops the mileage only about 2 mpg. That’s fairly level running in the east, but includes the Adirondacks.


Your Outback mileage may vary
from mine. Although maybe air flows better over longer boats than it does over ww kayaks.

Whitewater kayaks and c-1s seem to ride smoother if stacked on edge and positioned cockpit to cockpit.

East has lower speed limits
70 to 75 mph speed limits are common on highways in the interior west. That’s what’ll kill rooftopping mpg.