MPG With roof rack and bikes

[ronnie1995]

Hi all,
Hope you and your cars are doing well.

Just wondering what sort of mpg decrease there would be if I use the roof rack and bikes on a road trip?

I have the genuine vauxhall cavalier ones.

Some websites say only a couple to a few mpg but others suggest it will be almost 50%.

Does anyone have experience in this with their cav?

Mine's a 1.8i.

[humbucker]

Any roof bars or additional upper mass will increase mpg due to the additional drag (and weight, depending on how heavy your bikes are!).

[Cavalier342]

Depending on extra weight and driving style, you can knock anything from 5% to 10% from your average MPG return. Unless you rag it, it won't drop awfully much.

Just for reference, I can't say I noticed much economy change when towing a trailer in my V6, loaded or unloaded.

[thegriffin]

It denpends on how fast you drive and the direction
of the wind. In my TD on a 400 mile round trip to
Cornwall my mpg went from 52 to 45.
I recall on one trip into a strong headwind having to
use power down long hills where usually I'd be on the
brakes.
Keeping the empty bars on made little difference apart
from the noise.

[ronnie1995]

Okay that seems to not be such a significant difference, will just bear in mind to keep my foot up a bit more than usual haha