Roof Box Drag Effects on minivan MPG

[charlesj]

Have always been a roof box user. Until recently only with cars (old Passats, Saab 9-5) Never cared too much about the effects of drag because I needed a roof box. Have an old Sienna awd with snows now that I will be sleeping in periodically, so in theory I could put a few pairs of skis inside and not use the box. Did a few 1k mile trips with and without the roof box. Based on gut I figured there would be *some* difference. Same shitty 20-21 mpg highway with or without.

What are your results with and without?

edit: my OG AWD Sienna is 2004 (3.3l)

[joeshek]

Sequoia gets 16mpg with or without.

[fleaches]

FWD sienna was getting 28 highway without, more like 24 with.

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[charlesj]

FWD sienna was getting 28 highway without, more like 24 with.

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what year? any other variables? that's a significant difference.

[toast2266]

Kinda tough to figure since the roof box goes on at the same time my winter tires go on and around the same time we switch to winter blend gas.

But I figure the box takes my Allroad down about 1.5 mpg.

[Name Redacted]

My old truck actually improved gas mileage somewhat. Otherwise, there was negligible difference on our Outback.

[doebedoe]

I dropped 1-2mpg with roofbox on my 2013 FWD Sienna. Lift and tires stole another 1-2. Now low-mid 20s, previously mid-high 20s

[fleaches]

what year? any other variables? that's a significant difference.

2019, and you're right probably not exactly apples to apples. Had gotten 27-29 during several cross country interstate trips last year, and the one with the roof box was the interstate part of a CA<-->BC trip and I was pretty surprised by the low milage. Different tires might also be part of it, but they aren't oversized or anything. I'll have to do some A/B testing on the same route/conditions at some point this winter, but I usually don't have the box on since it's too short for most of my skis anyways.

I'd say it's pretty similar to the drop I get with kayaks on top but those are more air resistant than a box.

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[whyturn]

VW Alltrack with Thule frontier 13
30 without and 29 with


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[Squirreljam]

Got two odysseys, 09 and 20. The 09 drops about 1, 1.5 mpg with a Yakima 16 (but that’s not accounting for the fact that if I’ve got a box full of skis, I also have 5 people and ski gear IN the car so the net drop from the box only is likely less). 20 odyssey seems to drop less and has way better mileage overall.