Does Driving Slow or Fast Save Gas?

Given the current cost of fuel, you’re probably looking for ways to get a few extra miles out of a tank of gas. One of the first questions many drivers ask while thinking about mileage is what happens to the fuel when we drive too fast or too slow. You can actually save gas just by how you drive.

Driving Too Fast

Now, we all know that the mileage on a highway is almost always better than the mileage you get driving on city roads. This leads a lot of drivers to automatically assume that driving faster is better. Well, not exactly.

Most cars in the United States function really well when they are running between 50 and 60 miles per hour. This is because they are driving a constant speed at a low engine RPM. It takes much less fuel to maintain a vehicle’s speed than it does to accelerate.

Since every manufacturer wants to get the best MPG ratings possible, they make cars that run their best at certain speeds that they know the government tests every automobile at. If that testing happened at 30 miles per hour, every car would give optimum performance at that speed.

Now, when the vehicle hits 60 miles per hour, the gas mileage tends to drop off quite a bit. It is actually a lot more than most drivers realize. This is because the engine is working a lot harder to push through the air, so it needs a lot of fuel to maintain a faster speed.

If you have an onboard computer that displays instant gas mileage, you must check it out at 60 mph and then again at 80 mph. You should notice a big difference in fuel economy. 

Typically, a four-cylinder car will have an average of about 30 miles per gallon at 60 mph. But when you hit 80 mph, the mpg may fall to 20 mpg. Your gas mileage at 80 mph on an open road like a highway with no stops is not all that much better than the mileage you get while navigating red lights and traffic in the city.

The best way to find out when your car is giving its best is to look at the tachometer instead of the speedometer. A tachometer measures the rotation speed of the engine’s crankshaft and displays the revolutions per minute (RPM).

This tells you how hard your engine is working and helps you select the right amount of throttle and gear settings for the existing driving conditions. What you need to do is figure out the lowest RPM in the highest gear to maintain the best fuel economy, without lugging the engine. This way, you will be able to get the most out of the current speed without torturing the engine of your car.

Driving Too Slow

People often think that driving too slow helps save on gas. Well, that’s not always true either. When you have to speed up and slow down often, such as heavy traffic, your car does not give you the best results.

If you are driving a stick, you can help yourself and your car a lot more by knowing the best gear for each speed range. This also helps you match your car’s optimal performance when you are driving below 50 mph. That takes a level of skill, and most cars today have automatic transmissions anyway. Automatics switch to a better gear for fuel economy all on their own.

The ideal fuel economy numbers are typically seen between 30 to 50 mph, mostly due to gearing. When you go below that, the engine may end up burning more fuel. If you must drive slow, try to go a constant speed to maximize your fuel economy. If you speed up and slow down often, you are back to burning excess fuel.

According to the US Environment Protection Agency (EPA), you can save at least 20 percent more gas by staying between 40 and 50 mph.

Now, it is important to remember that this moderate speed is not the same for all cars. It is different for each model, because different cars have different gear ratios and numbers of gears. It’s also important to stay within speed limits.

So, if you are driving too slowly for the current gear, you will be putting a strain on the engine. This is called “lugging the engine”. If you have the air conditioning or the heater on for a long period of time, your engine will have to supply power to that, too.

All of these little factors result in an increase in fuel consumption. If you are looking to reach your destination on time while maintaining your car, the best thing to do is to drive within speed limits while paying attention to the fuel economy recommendations mentioned in your owner’s manual. 

Fuel Economy Tips

Here are some quick ways you can improve you fuel economy without a single modification to your vehicle.

1) Braking

Every time you apply brakes, you kill the forward momentum that your car has already achieved. If you find yourself braking unnecessarily, especially because you are always going too fast, you are killing your fuel economy numbers.

Excessive braking is a very common mistake caused by following the vehicle in front of you too closely. This may also happen when taking off at a traffic light. You accelerate too much too soon and then have to apply brakes because the car in front of you hasn’t picked up speed quite the way you did.

The best way to avoid this issue is to keep a keen eye on the traffic and anticipate the behavior of other drivers, then slow down accordingly. This way, you save gas money and coast to a slower speed instead of braking abruptly. Your drive remains gentle and you will get to your destination sooner without burning a lot of gas. You’ll also improve traffic flow, and the drivers behind you will thank you.

2) Coasting

Coasting is the process of letting the car lose momentum by taking your foot off the accelerator. This can help reduce the need to apply brakes, and is great for fuel economy.

When you coast, the fuel injectors shut off and you quit burning fuel. The engine spins because it is connected to the wheels, so you don’t burn any fuel to keep the car on. By observing traffic keenly, you can do this more often than you think and stay safe.

3) Tire Pressures

Tires are the most important part of your vehicle, and the only part that should be touching the ground. Check your tire pressure routinely, inflating them according to the specification on the driver’s side door jamb.

When your tires are underinflated, you end up burning more fuel to overcome the increased rolling resistance. Maintaining your tires is one of the first steps you should take in improving fuel economy. 

In Conclusion

The fuel consumption of a car highly depends on the way you drive it. You don’t save gas just by driving fast or slow. You do so by understanding the optimum speed of your car, the terrain you are driving on, and following speed limits. There are many steps you can take to maximize your fuel economy in any situation.