Last summer I got an overall 30mpg from my TDi (note the small i as it's a Seat) coming back from Brittany at about 80 - 85 mph. The car had a roof box on and was fully loaded with air-cond going full blast. On the way there I got high 30's, but my speed never wet above 60mph as I was still running it in (Yes, I know they say it's not necessary, but I've always done it and always will - I've never had a car that uses oil between services so it must be doing some good). My guess is that it might have increased fuel consumption by 10%, but what's the alternative? A trailer is more expensive as well as increasing your crossing costs if you go abroad. I store my roofbox in the garage - hang it from the roof of the garage by fixing eyebolts with rope which fixes to the bars, if you've got enough space. On holiday I take it off and store it in the garden of where we stay, although most GB's leave them on - you spot them everywhere! Putting it on / taking it off the car is a bit more difficult - a two person job for us - luckily I'm 6ft and my wife 5ft 10 - if you're shorter you will have a problem. I'm not sure about using ladders - if you slip it could be expensive. I've now bought a larger roofbox which is much heavier - too heavy for my wife to manage so I'll have to be nice to my neighbour - fortunately he also has a Alhambra. My personal preference is Thule roof bars - they're not the cheapest, but also not as expensive as the manufacturers ones. They are flexible - for example the bars I had on my Spacewagon were too short for the Alhambra - I just needed to replace the bars for