Trailer vs. Roofbox

[Commander]

I was wondering if anyone has compared the fuel consumption penalty between towing a luggage trailer vs. having a roofbox (Thule or similar) on the roof rack?
I have done a bit of long distance with a Venter 6 foot trailer (actually too big for my needs) and I was surprised at how big a difference it makes (looks like 1.5l/100 Km at 125km/h). This got me thinking on how a roofbox would compare.

Has anyone done the comparison?

[hatjohan]

In terms of volume and weight capabilities, you cant really compare the two.
See the discussions elswware on the weight limitation of roof racks

[Robbief]

Huge difference in volume.

[Commander]

Thanks, I was asking regarding fuel consumption specifically and I did say a trailer was actually much too big for my needs.

I probably wouldn't use a roof box as I have access to a trailer and the capital expense of a roof box would probably take many years to save in fuel (if it is actually more economical to use).

I was actually just wondering if anyone has tried both and what the fuel consumption penalty is for a roof box.

[Robbief]

According to google, 20 to 35% increase in fuel consumption for a roofbox.

[Commander]

Did some google searching as well as searching the forum and it seems results vary wildly depending on vehicle and speed travelled. I guess that result is to be expected, so only real way to get an answer would be to rent a roof box and test on my own vehicle.

[zx14]

I have the Thule xxxl roofbox.

On the Treg it makes about 0,5 liter/100km difference at 110.

[heyyahhey]

Did some google searching as well as searching the forum and it seems results vary wildly depending on vehicle and speed travelled. I guess that result is to be expected, so only real way to get an answer would be to rent a roof box and test on my own vehicle.

I have a mid-sized Thule - you’re more than welcome to borrow for testing etc... DM if interested - it’s in Midrand. Not sure the model but it’s about 45% the width of a typical roof, and a bit longer than a typical roof. Holds 4-6 duffle bags. We used it on a Q-5, but I never really paid attention to fuel penalty. It wasn’t much.

[Commander]

I have a mid-sized Thule - you’re more than welcome to borrow for testing etc... DM if interested - it’s in Midrand. Not sure the model but it’s about 45% the width of a typical roof, and a bit longer than a typical roof. Holds 4-6 duffle bags. We used it on a Q-5, but I never really paid attention to fuel penalty. It wasn’t much.

Thanks very much that would be very helpful to test in real world conditions, I will drop you a PM!

[Commander]

I have the Thule xxxl roofbox.

On the Treg it makes about 0,5 liter/100km difference at 110.

Thanks, this is very helpful Errol!

[Robbief]

Did some google searching as well as searching the forum and it seems results vary wildly depending on vehicle and speed travelled. I guess that result is to be expected, so only real way to get an answer would be to rent a roof box and test on my own vehicle.

And Ill supply you a trailer for the test, both to be empty.

Will be a worthwhile test.

[Commander]

And Ill supply you a trailer for the test, both to be empty.

Will be a worthwhile test.

Thanks, I am keen to do that also, I have used my dad's 6ft Venter on hunting trips (empty and then somewhat loaded on the way back) and have noticed that there is quite a big difference between 125km/h and 115km/h on the open road.

[Recovery]

I have a Thule roof box, can take say 5 60lt duffle bags. Took it to mana pools. Not as big as a trailer, but from a fuel efficiency point of view I recon it added maybe 0.2 Lts /100kms. Cruising speed aprox 110 km/hr