Roof Racks are designed to carry bulky, but light weight items. Remember that the bulkier the item, the worse your fuel economy is going to be. However, if it means that you can take the item with you as a pose to leaving it at home most people will pay the extra fuel. It can help to fit a wind deflector, but it depends on the racks that are fitted. The primary benefit of racks is the additional storage that you gain. However, they can be used for mounting spotlights, work lights and general fairy lights if that is what you choose to do.
Most racks can be removed during periods that you don’t use them (most people don’t use them in between holidays) and this will save you a reasonable amount of fuel (usually in the realms of 1.5 – 3 litres per hundred kilometers). It pays to remove them where practical, but sometimes they are just too difficult to get off and on regularly. One of the major advantages of a roof rack is you have the option of fitting a roof top tent. These are great for setting up camp quickly, and they get you off the ground and away from the insects and other animals. When looking to purchase roof bars, think about what you are going to carry on top, how much room you will need, how high they sit and the price. The well known brands are popular for a reason, and believe me there are some terrible quality roof bars, baskets and racks around. If you get something that is poor quality you need to expect to have to replace it sooner than later!