Portuguese 
English 
Spanish 
4 min of reading 
2 comments 
Three Common Practices That Many Drivers Believe Help Save Fuel May Actually Increase Consumption And Even Compromise Safety While Driving.
Many people believe that small daily practices help to save fuel.
These are tips passed down from generation to generation, shared by experienced drivers or in groups on social media. However, despite being popular, some of these ideas simply do not work. Worse: they may even have the opposite effect.
Three myths stand out due to how often they are repeated. The first is the habit of refueling the car early in the morning, under the belief that fuel yields more.
-
Renault Espace F1 put a Formula 1 V10 with 820 hp inside a 4-seater minivan, exceeded 300 km/h, and became one of the craziest automotive experiences ever built.
-
Jetour hybrid SUV targets Brazil with 360 hp, 6 or 7 seats, and a range of 800 km, as the Chinese brand prepares to compete with Haval H6 and BYD Song Plus in the family plug-in market in 2026.
-
In the range of R$ 35,000, consumption of up to 22 km/l, 1.0 three-cylinder engine, electric steering, 8” multimedia, four airbags, and over 80% of national parts with low maintenance costs: meet the Renault Kwid 2026.
-
Changing the 5W30 oil to 10W40 to “compensate for clearances” after the Corolla surpasses 150,000 km can damage the engine, warns a technical consultant.
The second is putting the car in neutral while going downhill, thinking it saves the engine.
The third is driving with the windows down, imagining that this helps avoid the consumption generated by the air conditioning.
Understand why these practices do not guarantee savings — and how they may even hinder you.
Refueling In The Morning Does Not Yield More
This is one of the oldest and most widespread myths. The theory seems to make sense: with lower temperatures in the morning, the fuel would be denser and therefore yield more when refueled. However, this reasoning does not apply in practice.
The tanks at gas stations are buried underground. This means that their temperature remains virtually constant throughout the day.
In other words, it does not matter if the refueling happens at 6 a.m. or 4 p.m.: the amount provided will be the same.
Even in extreme cases, the variation in density is so small that it does not significantly interfere with consumption.
No driver would notice a real difference in their wallet just because they chose to refuel early. Therefore, refueling in the morning does not make fuel yield more and does not help save fuel effectively.
Putting In Neutral While Descending Only Makes It Worse
Another common practice among drivers is to put the car in neutral while going downhill.
The idea is simple: if the car is “free,” without forcing the engine, consumption would be lower. But the reality of modern cars disproves this logic.
Vehicles with electronic fuel injection automatically cut off fuel delivery when the car is in gear and the driver lifts their foot off the accelerator.
This means that, when descending a slope with the gear engaged and without accelerating, the car practically consumes nothing. The engine runs by inertia, without needing fuel to keep functioning.
In neutral, however, the engine needs to maintain idle speed. To do this, it continues injecting fuel all the time.
In other words, contrary to what many believe, the car consumes more when it is in neutral than when it descends in gear without accelerating.
Moreover, there is a safety issue. With the car in neutral, the driver loses the so-called “engine brake.”
This increases the effort on the brakes and can cause overheating on long descents, putting safety at risk. Therefore, in addition to not helping save fuel, this practice can be dangerous.
Open Windows Are Not Always A Solution
Another popular myth is the use of open windows as a way to save fuel. The logic here is to avoid using the air conditioning, which indeed consumes more engine power. But just like in other cases, the situation is more complex than it seems.
At low speeds, such as in urban streets or in traffic jams, opening the windows does not significantly affect the car’s aerodynamics.
In these cases, it may indeed be advantageous to keep the air off and take advantage of natural ventilation. However, the situation changes completely when the vehicle is at high speed.
On highways or fast avenues, driving at 50 mph or more, open windows create wind resistance, known as aerodynamic drag.
This resistance forces the car to use more energy to maintain speed, which increases fuel consumption.
Therefore, at high speeds, keeping the windows down may result in equal or even greater fuel consumption than using the air conditioning.
The ideal is to find a balance: use the windows at low speeds and turn on the air in faster stretches when necessary. Real savings depend on the situation, not a fixed rule.
Economy Depends On Consistent Habits
The truth is that saving fuel does not depend on isolated tricks, but on consistent and conscious habits. Keeping the car well-maintained, checking tire pressure, avoiding sudden accelerations, and respecting speed limits make more of a difference than following popular myths.
Refueling in the morning, using neutral on descents, or opening the windows does not guarantee savings. On the contrary, these attitudes can have the opposite effect or even compromise safety. The best way to spend less fuel continues to be driving in a balanced manner and keeping the vehicle maintained.
Even simple actions, like avoiding leaving the car idling for too long or knowing when to shift gears, contribute to more efficient consumption. Unlike the myths, these practices yield real results.
With so much information circulating, it’s always important to verify what really works. When in doubt, the best path is to consult the vehicle’s manual and follow the manufacturer’s recommendations. Savings come with responsibility, not with magic formulas.
Na descida, quem coloca o carro no neutro, também não usa o acelerador! Sendo assim não está havendo injeção de combustível!
Já o veículo engrenado, a inércia vai fazer o motor subir de giro, daí o sensor de rotação vai avisar a centralina. O motor será parcialmente alimentado! Agora.. sobre segurança, não há dúvidas que é mais perigoso descer na famosa banguela!
Meu carro é um Sandero Stepway 2014 e é automático pois sou PCD na questão de descida eu não o deixo em D pois ele só usa a ” segunda marcha” e dependendo da via eu coloco no modo manual e deixo em ” terceira ou quarta” assim da diferença no consumo.
Para frente pretendo pegar um carro melhor e mais novo.