Originally written: 03-25-2007, 08:44 PM
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Waaaay back in the summer of '06 I did a few runs to look at the effect roof racks have on fuel economy.
Originally, this came up in a thread about a cyclist using his Yaris to carry bikes to races he was attending.
(Note: zooms don't work here - go to MetroMPG.com if you want to see the bigger versions.)
I finally got around to posting details of the "test" (not exactly rigorously scientific) and some pics on MetroMPG.com. Here's the summary:
From:
Mini-experiment: the wrath of roof racks (MetroMPG.com)
The comparison was between:
- A - no roof racks
- B - empty roof racks
- C - a mountain bike on the roof racks
Results:
- Average of all 'A' runs: 55.24 mpg (US)
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- Just adding (empty) roof racks reduced fuel economy to 48.2 mpg (US), or -7.0 mpg / -12.7%.
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- Putting the mountain bike on the rack absolutely destroyed the mileage! Down to 40.1 mpg (US), or -15.1 mpg / -27.3%
Also posted some corroboration about the severity of the effects from other people:
Such as the Prius owner who saw his mileage drop from 47 to 36 mpg (US) with a kayak up top.
And Peakster's mini-experiment posted here at GS about the effect of driving with your hatchback wide open:
hatch-propped open vs. hatch-closed
For all the gory details:
http://metrompg.com/posts/roof-racks.htm