Drivers can pay “lower prices” at fuel stations across the UK by making an easy change - but it might not be for the reason they think, say experts.
As petrol and diesel prices have rocketed in recent years, drivers are more aware than ever of trying to shave a bit off each tank of fuel. many will have heard the tip that filling up at night, when the air is cool, get more fuel for your money, as fuel expands when heated making the liquid less dense.
But, most petrol stations store petrol or diesel underground in large tanks which keeps the fuel at a constant temperature.
"A common myth is that filling up your car late at night, when the air is cooler, saves money because the fuel is denser," says Fuel expert Gordon Wallis from Interfuels.
"While temperature does cause slight changes in fuel volume, the effect is tiny – usually just a few pennies per tank. Over time, careful drivers might notice a small difference, but it’s not significant enough to make a real impact."
But, filling up outside peak hours can be cheaper for a different reason.
“The time of day can still make a difference," says Gordon.
"Fuel prices are often lower late in the evening or early in the morning when demand is low. On the other hand, prices can be higher – and queues longer – around midday or after 5 pm, when most people are stopping to refuel after work."
How about tank volume and fuel efficiency - is a full car less efficient?
"Filling your car's tank completely does add weight, but it's a small amount – typically less than 5% of the car's total weight – so the difference in fuel efficiency between a full and half-full tank is likely to be minimal, and you might not see much change at the gas station," says Gordon.
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How about running low on fuel - is that bad for your engine?
Again, it's more about a cost issue than a physical one, says Gordon: “When your fuel gauge hits 50 miles left, think refuelling. This gives you plenty of time to find the best fuel prices, rather than being rushed into a decision as your tank nears empty.
“Running out of fuel completely can damage the fuel pump itself, especially if it runs dry, as it can be a costly fix. It's generally best to maintain at least a quarter tank of fuel to avoid these risks."
"Maintaining a healthy fuel level, rather than constantly topping up or running on fumes, is a more practical approach to fuel efficiency. By keeping your tank at least a quarter full, you can avoid any risks associated with low fuel levels and get rid of any potential efficiency drawbacks from a full tank."
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