In a week orso, I hope my roofrack with dust deflector will arrive from the States. I really wanted that as, in my opinion, it really finishes the car. I will find the answer as I am going on another Italy trip in a month (2500 mile roundtrip), but I was curious what you think that will happen. A. Will the roofrack just introduce more drag and lower fuel efficiency. B. Will the roofrack, and more the dustdeflector, deflect the air in the vacuum behind the car and increase fuel efficiency. C. Will both phenomena more or less cancel eachother out and I will not notice any difference?
I think it might help your mpg, but only slightly. Removing the rack entirely, which is what I did, will improve the mileage a noticeable amount.
But Andy, you have to tell him that the rack came off when granny's rocking chair flew off with her in it! She was the cause of the wind drag! That rear Dust Deflector does just that, keeps the dust and road spray away from the rear glass. So you might have a tiny loss from it. I can't see how the roof rack rails would have a big effect, but then I keep it under 100 MPH.
You won't see any change in fuel economy. But it should help keep the rear window cleaner. Plus I think it looks nicer with the rear deflector too.
The hypermiler crowd have actually proven that removing racks and dust deflectors reduce fuel consumption. The difference is so small you have to ask is it worth the effort? Personally I prefer to keep the deflectors, IF they work properly which isn't always the case. The deflector on my previous Commodore wagon worked very well at keeping the top half of the glass clear. The one on the current Verdada wagon is't as good, only keeps the top quarter clear. I'll be curious to see how the minivan goes in keeping the glass clear with no deflector. All 3 vehicles have roof racks, removed the cross bars on the Verada as they look awful and were corroded.
