When people choose a car with an eye on saving money on gas, they often lean toward models with low gas mileage.

But is it a simple rule that small-displacement cars always have low gas mileage, while large-displacement cars have high gas mileage?

In a broad sense, larger displacement cars do tend to have lower gas mileage. This is because larger displacement car engines often have lower efficiency. When an engine is less efficient, it requires more fuel to perform the same amount of work. It's akin to a person doing hard work in the morning and needing a hearty meal at noon to replenish their energy. Conversely, if the work is done slowly throughout the day, they might need three meals to sustain them.

However, when we examine this issue strictly from a scientific perspective, the conclusion becomes less clear-cut. Displacement, in and of itself, does not have a direct correlation with gas mileage.

Displacement refers to the volume of exhaust, the volume of cylinder work, and the space swept by the piston from the top dead center to the bottom dead center. It depends on factors like cylinder bore and piston stroke.

Engine displacement is the sum of the working volumes of the cylinders, and the greater the combined volume of the engine's cylinders, the larger the displacement.

So, what are the primary factors that influence fuel consumption?

1. Engine Technology: Modern engines come equipped with various technologies such as VVT and DVVT. These technologies primarily aim to enhance the conversion of fuel kinetic energy into power, ultimately improving fuel economy.

To meet user demands and increasingly stringent emission standards, automobile manufacturers continually innovate engine technology. Choosing a more advanced technology engine can result in better fuel efficiency.

2. Vehicle Weight: The weight of a car affects the force needed to drive it. According to the law of conservation of energy, more work requires more fuel consumption. This is why larger vehicles like SUVs tend to consume more fuel.

3. Resistance: Resistance encompasses various factors such as air resistance, transmission resistance, friction resistance, and tire rolling resistance, all of which impact fuel consumption.

Air resistance, also known as wind resistance, is especially significant and is often measured in wind tunnel tests during vehicle development. Reducing wind resistance can significantly contribute to fuel savings, which is why many car manufacturers highlight their vehicles' wind resistance coefficients in product brochures.

While there is a general trend that larger displacement cars consume more fuel, the relationship between displacement and gas mileage is not as straightforward as it may seem.

Modern advancements in engine technology, vehicle weight reduction, and the management of various forms of resistance all play a crucial role in determining a car's fuel consumption. Therefore, when choosing a fuel-efficient vehicle, it's essential to consider these factors alongside engine displacement.