Here’s How Much a Rooftop Carrier Killed Our Gas Mileage

by Darwin on July 23, 2013


We recently took a trip to the the Carolinas and traveled ~1000 miles round-trip.  Because we aren’t very good at prioritizing our “stuff” both in our home and when we travel, we’ve had to resort to the dreaded roof-top carrier whenever we vacation.  I always feel like we overpacked once we get there but oh well, at least we’re prepared… but that comes with a cost.  Out of curiosity, and after inexplicably running out of a full tank of gas rather quickly, I decided to do an experiment.  While at the pump, I took a look at the distance back home (love that iPhone!) since we had just completely filled our tank before leaving and we arrived at the gas station completely on E.  I then looked at the pump to see how many gallons we just purchased to refill it and there it was. A measly 14.7 miles per gallon for our 2009 Honda Odyssey.  In looking at the mpg for standard highway driving, this model should get 23 mpg.  This roof top carrier thus resulted in a whopping 36% reduction in our gas mileage.  That seems pretty hard to believe that was lost fully 1/3 of our gas mileage, but that’s what the data shows.

We’ve been borrowing our friends’ roof top bag like this one.  They’re pretty cheap at less than $100 for many models and a good starter carrier, but I could see how they definitely result in a lot of drag.  Since they’re flexible, the wind eventually pushes everything up in the front and it eventually looks all scrunched up and like a giant box on the top of the van.

Cost in Dollars

Back to the inefficiency of the rooftop carrier in general. Had we not needed it at all, we could have gotten by with 36% less gas for the trip.  The cost with the carrier for the 1000 miles driven at ~$3.50/gallon was $238.  At regular mpg without a carrier, the cost would have been reduced to $152 for a difference of $86.

So, question answered.  For each 1000 miles driven, expect to pay close to $100 extra in gas for a minivan at today’s gas prices.  If you’re making a couple trips per year and want to save a few hundred bucks a year, perhaps it’s cost-effective to figure out a way to get more stuff in the car, pack less, or even a Thule hard-top might be more fuel-efficient.  Don’t forget, you can hedge your gas spending like I do quite simply (this has worked out wonderfully for us).

Do You Use a Carrier?

Does the Mileage Loss Bother You?

{ 1 comment… read it below or add one }

Michael July 28, 2013 at 12:06 am

It’s not accurate to compare to the EPA figure. You should measure actual has mileage on a highway trip without the roof top carrier. Very unlikely the carrier is reducing gas mileage by 36%.


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