Asda, Morrisons, Tesco and Sainsbury's drivers warned 'remove roof rack'

Motorists heading to fill up their vehicles at Tesco, Asda, Morrisons and Sainsbury's have been advised to remove any roof racks from their cars first. This guidance comes in an attempt to boost fuel efficiency.

Sam Sheehan, the motoring editor at cinch, reinforced this advice by stating: "Roof bars and roof boxes can create wind resistance, causing your vehicle to waste more fuel because of the so-called 'drag' effect."

He explained further: "According to studies, an empty roof rack can increase drag by about 16 per cent at 75mph, while an unused roof box adds up to 39 per cent more." Leaving these attachments on could mean you end up using significantly more fuel, reports Birmingham Live.

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As such, he advised: "So, if you're not using your roof bar or roof box, remove it to save money and minimise your emissions." Additional research from industry experts at What Car? True MPG confirms that vehicles with roof tracks might see a 27 per cent drop in fuel efficiency.

However, despite the obvious space-saving benefits of a roof box, they may not be a budget-friendly option, with prices starting at £130 and going as high as £750. Additional kits, foot packs and roof bars could add another £200, which doesn't include potential professional fitting costs.

Jim Holder, editor of What Car? said: "The vast majority of cars are unable to match the official MPG figures that manufacturers quote even before the addition of a roof box. Adding the box increases the overall weight of the car and increases aerodynamic drag, so it stands to reason that your fuel efficiency will be harmed.

"Taking a break in the UK might be considered a sensible thing to do in order to save some money but you're effectively paying for it in other, less obvious ways."