Some drivers claim that faster driving helps save fuel, while others advocate for slower speeds. So which approach actually works better?
In various conversations about cars and fuel economy, you might hear people argue that driving faster will get you to your destination quicker, spending less time on the road and therefore burning less fuel. Others will firmly insist that the slower you drive, the less fuel you’ll use. Who should you believe?
The science behind speed and fuel consumption
According to a comprehensive study by the New Zealand Transport Agency, driving at approximately 55 mph is about 23% more fuel-efficient than traveling at 68 mph, and a full 30% more economical than driving at 75 mph.
The primary reason is that higher engine RPMs force your motor to work harder, resulting in greater fuel consumption. Plus, faster driving means your vehicle faces increased aerodynamic drag – the resistance from the air pushing against your car as it moves. (Ever tried sticking your hand out the window at 70 mph versus 40 mph? You can literally feel the difference!)
The sweet spot for fuel efficiency
However, extremely slow driving might not save much fuel either because the engine isn’t operating in its optimal RPM range. For example, when you maintain a steady speed of 37-43 mph, your engine will typically consume more fuel than if you were cruising at 55-62 mph. Why? Because your transmission might not shift into its highest gear (whether automatic or manual), causing the engine to burn more fuel than necessary.
So what’s the answer? Moderate, consistent speeds will help you save the most fuel. Most modern vehicles achieve their peak efficiency somewhere between 50-65 mph on highways, though this varies by make and model. Have you checked your car’s fuel efficiency curve in the owner’s manual? It might surprise you to learn where your specific vehicle performs best.
Beyond speed: Other factors affecting fuel consumption
Regular maintenance of your vehicle, such as oil changes and tire pressure checks, will also help minimize fuel consumption. Underinflated tires can reduce fuel economy by about 0.2% for each 1 psi drop in pressure of all four tires. The rolling resistance increases as tire pressure decreases, requiring more energy – and thus more fuel – to keep your car moving.
Selecting the right gear can significantly impact fuel economy too. With a manual transmission vehicle, you should choose the gear appropriate for your speed and traffic conditions, allowing the engine to operate efficiently. Modern vehicles often have gear shift indicators to help drivers optimize shifting points for maximum efficiency.
Smart driving techniques for better mileage
Beyond just your cruising speed, how you accelerate and brake makes a huge difference. Gradual acceleration and anticipatory driving that minimizes unnecessary braking can improve your fuel economy by up to 30% in some driving conditions.
Using cruise control on highways helps maintain a steady speed and avoid the fuel-wasting acceleration and deceleration cycles that happen when speeds fluctuate. Did you know that each time you brake, you’re essentially wasting the fuel you used to get up to speed in the first place?
Air conditioning use can increase fuel consumption by 1-4 mpg, depending on your vehicle and outside conditions. At lower speeds (under 40 mph), opening windows instead of using AC is more fuel-efficient. However, at highway speeds, open windows create enough drag that AC might actually be the more efficient choice.
Finding your vehicle’s efficiency zone
Every vehicle has its own efficiency sweet spot based on its weight, aerodynamics, engine design, and transmission gearing. Newer vehicles with trip computers make it easy to track your real-time fuel consumption, allowing you to experiment and find the most efficient driving style for your specific car.
In the end, driving at sensible speeds – not too fast, not too slow – while maintaining your vehicle properly and using smooth driving techniques will help maximize your gas mileage. Your wallet (and the environment) will thank you for it.
