As summer approaches, millions of holiday-makers will soon take to the world’s highways. Owing to the laws of supply and demand, the increase in vehicles invariably causes a spike in fuel prices.

It prompted us to visit, the online question and answer community, to find out how users get the most out of every tank of gas. Not every respondent had the same approach, but most had simple tips that could keep a driver on the road longer between fill-ups.

Light makes right

Alex Elderfield noted that excess weight prevents an engine from burning fuel efficiently. "Only carry what is essential in your car, clean out any junk or necessary items otherwise you are paying for the fuel to cart these from place to place," he wrote.

Driving smoothly – that is, not mashing the gas and then slamming the brakes later down the road – was a fixture of many responses. That advice resonated with Quora user Clint Law, who wrote, "Every little bit of kinetic energy that your brakes dissipate, your engine burned in fuel to [amass]." Excessive braking should consequently be viewed as squandered acceleration. "That's really what kills your fuel economy," he argued.

Keep the pressure up

Maintaining the recommended tire pressure for your car was another mantra among Quora users.

Marlyn Rosent said she checked her tire pressure every time she filled up her SUV. "I put new caps on that let me measure air pressure [without] unscrewing the little buggers," she wrote.

Quora user Doug Dingus checks his tire pressure every weekend. "Less tire contact means reduced friction, requiring less fuel," he said.

Air conditioning v windows

Though the summer heat prompts many drivers to roll up the windows and crank the air conditioning, some respondents argued that running the A/C wastes too much gas. In between were many shades of grey.

Achilleas Vortselas said it would depend largely on a car’s speed. He wrote that as a general rule, people should drive with the windows down around the city and turn the air conditioning on when hitting the highway, where a car’s aerodynamic attributes would be compromised by opened windows.

More ascetically minded respondents, however, said to travel as much as possible with windows up and A/C off. Eddie Xue gets by with just a wisp of outside air. “Use the fan and crack your windows every now and then at lower speeds," he wrote.

But Jonathan Drake says there's balance between air conditioning and windows usage, and referenced the Mythbusters television series as his source. He argues that when a car approaches higher speeds, the A/C should come on. "This isn't super-technical, but Mythbusters visited this question twice. In their second attempt, they found that the break-even point was 50mph," he wrote.

Fuel efficiency, straight from source

Given the variety of opinions out there – some of which can smack of hunches rather than hard science – we cross-referenced Quora users’ suggestions with recommendations from ExxonMobil. As it turns out, many Quora users were spot on.

Exxon contends that reducing the weight in your car by 100lbs can increase the vehicle's fuel economy by up to 2%. Tire pressure also plays a critical important role. Dialling in proper tire pressure once a month can increase fuel economy by up to 3%, according to Exxon.

When it comes to smooth driving and braking, Quora users were right again. "Aggressive driving (speeding, rapid acceleration and braking) wastes gasoline,” Exxon noted. “It can lower your gas mileage by 33% at highway speeds and by 5% around town."

And as for driving with the windows down or using the A/C, Exxon recommends rolling those windows up and turning on the air conditioning at speeds of 60mph or greater, which reduces aerodynamic drag.

Of course, intrepid summer motorists can always practice “hypermiling” – a discipline that champions extraordinary driving techniques in the name of returning gaudy gas mileage. Even if you go that route, there’s no need for guilt when blasting that A/C (at least on the highway).

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