My gut feeling is at the speeds you are travelling at normally, not a great deal of difference.

I would have assumed that you need the rack for your work, but if you don't why not remove the thing anyway, alternatively look for another rack that has the two parallel bars only fixed, with clip in cross bars which take seconds to remove when not needed, obviously it needs to be sensibly priced (used?) because it might take a long time to recover the cost in any fuel saved...could you alter the present rack to make the cross bars removable?

I'd be jacking the van up and checking for dragging brakes, and checking the air intake is all clear.

Thanks for the replies!.

I would have already tried just taking it off, but was concerned about how much of a faff removing it would be, in particular i was thinking about all the interior roof trim and the clips. But having done some research, the trim clips look easy enough. I just wondered if anyone had worked out MPG with and without a roof rack, just to get an idea.

GB, as a 'pure water' window cleaner i don't use ladders, just the telescopic poles, so i don't actually need it for work. But due to various 'home improvement' projects over the next few years, it may well be useful to have. So i will have a look at the rack to see if the cross bars are removable, otherwise i may well look into the prices of the type you describe.

Andrew, yes you are probably right re the sealing, i just wasn't looking forward to what i thought could be an akward job getting the interior trim and rack off, but am a little more confident now that it shouldn't be too difficult.

bbd, does your roof rack making any whistling noises as you drive? My old roof bars on a previous car were square jobbies that were very annoying on the move above a certain speed.

I've got aero roof bars kept permanently attached to the Forester for work. They are tear shaped and are superb in comparison, absolutely silent. I know the car isn't exactly aerodynamic but I have noticed no extra drag since putting them on (I forget that they are on) where the square ones were terrible.

There are plenty of companies out there that make aerodynamic roof rack systems for vans, incorporating aids like rear rollers built into the back for sliding heavy ladders onto the roof.

Not that i am aware of, even when i drove it up from North West England to my home in North East Scotland. But the engine is quite vocal, to the point where i will at some point look at some kind of soundproofing!.

I remember Mythbusters on Sky doing an experiment to see whether certain myths were real regarding drag and mpg.

roof racks were the same as having windows open, the mpg was not affected enough to cause concern. ie, their was no difference in fuel consumption with either, only that some makers of roof racks were noisy