What results in increased fuel consumption of your car?

You answered correctly. Both a roof rack or ski rack, and transporting unnecessary objects, increase your car’s fuel consumption. This is because additional weight and increased air resistance require the engine to work harder, leading to higher fuel use. Excessive tyre pressure, however, does not increase fuel consumption; in fact, underinflated tyres are what usually cause higher fuel usage. Always remove unnecessary items and unused roof racks to save fuel, and keep your tyres at the recommended pressure.