Change in fuel economy with roof racks on A4 Avant?

Just for curiosity: Any of you with A4 Avant notice a worsening of fuel economy when driving with roof racks attached to the railings?
Strangely enough I appear to burn 5-10% more fuel with them on, even if
it's just the roof racks. Most of my driving is on the highway, avg speed approx 100 km/h (60 mph)
Any of you notice a difference? Or is just my imagination?
/Robert
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'appear to burn 5-10% more fuel'
How can you imagine a fact?
Ronald
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R@L wrote:

Very funny.
/Robert
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Indeed, your message was funny.
Ronald.
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Never bothered to calculate the difference in fuel consumption but I notice a lot more wind noise with them than without.
I would expect this increased drag to affect my fuel economy but I'm more picky about the noise than anything. I remove them when not in use.

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From another car type but maybe it applies:
With larger Jeeps like the Grand Larado it is suggested that the front rack be placed in the forward slot and the rear in the back slot. If I recall correctly, it was an economy (first) and noise (second) suggestion. This was mentioned in the owners manual (1999 vintage). Of course when you buy a Jeep now, the racks are not provided as standard equipment (rails yes, racks no) 2002 vintage.
HTH, Glenn

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Glenn Spence wrote:

Thanks Ken and Glenn. Good to hear that there may well be truth to my theory that roof racks, apart from the wind noise, were causing me to eat a bit more fuel. Didn't believe it at first when I went through my logbook. . . . /Robert
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Why is it strange? The car-manufacturers spend a lot of time and money on aerodynamics. Placing a horizontal bar (roof-rack) straight into the wind-direction makes this aerodynamics dramatically worse. You should only be carrying a roof-rack when really carrying something in it. Otherwise it just adds noise and fuel-consumption..
Daniel
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