Regan Brown
Whether or not a car uses fuel when coasting in gear is a highly debated topic among car enthusiasts. The general consensus is that coasting in gear is more fuel-efficient than coasting in neutral. When the transmission is engaged, the computer detects acceleration without throttle and cuts fuel to the engine. The engine continues to run, but the drive line turns it over instead of ignited air/fuel mixtures in the cylinders. However, some argue that coasting in gear can slow the car down, requiring more fuel to accelerate again. Additionally, modern cars with manual transmissions will cut off the fuel supply when the foot is taken off the accelerator, but the clutch is engaged, allowing the wheels to move the pistons.
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What You'll Learn
Coasting in gear vs. in neutral
Coasting in gear is when the transmission is still engaged, and the computer will detect acceleration without any throttle being applied, and it will cut fuel to the engine. The engine is still running, but the drive line is turning it over as opposed to ignited air/fuel mixtures in the cylinders. This allows the engineers to cut fuel completely when the vehicle detects this, resulting in zero fuel use.
Coasting in neutral, on the other hand, will cause the computer to detect no throttle input or gear engagement, and it will supply enough fuel to the engine so that it will idle. This means that the engine requires fuel to keep the vehicle idling. For example, when driving down a hill, you will use at a minimum the same amount of fuel and perhaps more because the engine is still working and the fuel is still flowing.
Coasting in gear is generally considered more fuel-efficient than coasting in neutral. When coasting down a hill with the car in gear, the engine no longer injects fuel and, consequently, consumes no fuel. In contrast, coasting in neutral will use a little more fuel as the engine requires fuel to keep the vehicle idling.
However, there is a scenario when coasting in neutral is more fuel-efficient. If you are rolling down a large hill and have enough momentum to roll over a smaller hill, it is more efficient to be in neutral. Additionally, coasting in neutral can be useful when coming to a stop as it is similar to being in an automatic.
It is important to note that coasting in neutral can be dangerous as it reduces vehicle control. When in neutral, you will not be able to accelerate and can only slow down via the brakes. This lack of control can potentially impact your ability to avoid hazards.
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Fuel efficiency of modern cars
Fuel efficiency in modern cars is a topic of interest for many, from car enthusiasts to environmentally conscious drivers. The way a car is driven and its maintenance can impact its fuel efficiency, and there are strategies to reduce fuel consumption.
One of the key factors affecting fuel efficiency is the driving behaviour. For example, aggressive manoeuvres such as sudden acceleration and heavy braking waste energy, leading to higher fuel consumption. Additionally, driving at extremely low or high speeds can also impact fuel efficiency. It is believed that cars achieve maximum efficiency between 40 and 50 mph (65 and 80 km/h). Driving at a steady speed can also improve fuel efficiency, as seen in a 2010 study where some vehicles achieved better fuel economy at 100 km/h (62 mph) compared to lower speeds.
The type of vehicle also plays a significant role in fuel efficiency. Larger and heavier vehicles, such as refuse trucks and transit buses, tend to have lower fuel economy due to their weight and driving cycles. On the other hand, electric cars do not directly burn fuel, so their fuel economy is measured differently, often using equivalence measures like miles per gallon gasoline equivalent.
Another aspect to consider is the transmission system. In modern cars with electronic fuel injection, it is more fuel-efficient to coast in gear than in neutral. This is because, when in gear, the engine does not inject fuel while coasting downhill, as the wheels and transmission are turning the engine over. However, if the car is taken out of gear, the computer detects the lack of throttle input and supplies fuel to the engine to keep it idling, increasing fuel consumption.
Lastly, regular maintenance and proper tyre pressure can also impact fuel efficiency. Under-inflated tyres can increase tyre drag, leading to higher fuel consumption. Therefore, it is essential to keep tyres properly inflated and maintain the vehicle to ensure optimal fuel efficiency.
In conclusion, modern cars have improved in fuel efficiency over the years, and by adopting good driving habits, understanding transmission systems, and maintaining vehicles properly, drivers can further enhance their cars' fuel efficiency.
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Engine braking
Coasting while driving refers to travelling either with the clutch pedal held down or with the car in neutral. This happens naturally for very short periods when changing gear and when coming to a stop. However, many drivers keep the clutch pedal held down or the car in neutral for extended periods because they believe it saves fuel.
Modern cars with manual transmission will cut off the fuel supply when the foot is taken off the accelerator. When the transmission is still engaged, the computer will detect acceleration without any throttle being applied and will cut fuel to the engine. The engine is still running, but the drive line is turning it over, as opposed to ignited air/fuel mixtures in the cylinders. If the car is taken out of gear, the computer will detect there’s no throttle input or gear engagement and will supply enough fuel to the engine so it will idle.
Therefore, if you are travelling at a speed that can be maintained without using the accelerator, you are better off staying in gear for the purpose of saving fuel. This is because, when in gear, the engine no longer injects fuel. Consequently, the engine consumes no fuel when rolling downhill and is only turned over because the wheels and transmission are forcing it to. On the other hand, if you were to coast in neutral, you’d use a little more fuel because the engine requires fuel to keep a vehicle idling.
One scenario when coasting in neutral is more fuel-efficient is when you roll down a large hill and have enough momentum to roll over a smaller hill while still in neutral. If you were to attempt this in gear, a car would use no fuel going down the first hill, but the engine braking would force the driver to accelerate up the second hill, thus using more fuel.
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ECU fuel supply
The ECU, or Engine Control Unit, is a crucial component in modern vehicles, as it controls the fuel supply and other parameters for optimal engine performance. When it comes to fuel efficiency, the ECU plays a vital role in managing fuel injection, ensuring the engine receives the correct amount of fuel.
Modern cars with manual transmissions will cut off the fuel supply when the driver removes their foot from the accelerator, even if the car is still in gear. This is made possible by the ECU, which detects that no throttle is being applied and responds by cutting the fuel supply to the engine. This means the engine is still running, but it is being turned over by the drive line rather than ignited air/fuel mixtures in the cylinders.
The ECU's ability to manage fuel supply is especially advantageous when coasting downhill in gear. In this scenario, the ECU detects acceleration without throttle input and subsequently cuts the fuel supply to the engine. As a result, the engine consumes no fuel while the car rolls downhill, improving fuel efficiency.
The ECU's role in fuel supply is further enhanced by its ability to communicate with various sensors. For instance, O2 sensors provide the ECU with information about the air-fuel ratio, allowing the ECU to adjust the fuel supply accordingly. IAT sensors inform the ECU about the temperature of the air, enabling the ECU to compensate by providing more fuel when the air is colder and denser. Additionally, ECT sensors notify the ECU when the engine has warmed up, prompting the ECU to activate the cooling fan or advance the ignition timing.
Overall, the ECU is integral to the fuel supply system in modern vehicles, particularly those with electronic fuel injection. Its ability to process sensor data and adjust fuel injection accordingly ensures optimal engine performance and fuel efficiency.
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Driving manual vs. automatic cars
There are two types of transmission in modern vehicles: automatic and manual. In a manual transmission, the driver is responsible for shifting the gears, while an automatic transmission vehicle does the shifting for you.
Manual Transmission Cars
Manual transmission cars are less common than vehicles with automatic transmission, accounting for less than 3% of sales in the United States. They are, however, popular in Europe and Asia, with over 80% of vehicles sold being manual. Manual transmission cars are usually cheaper to buy, less expensive to service, and more fuel-efficient than automatic cars. They are also preferred by performance drivers for the control they offer. However, they require more practice to learn and can be difficult to drive in stop-and-go traffic.
Automatic Transmission Cars
Automatic transmission cars are easy to use and require less driver input. They are popular in the US, with 95% of cars sold having automatic transmissions. They are also widely available and have a higher resale value. Improvements in technology have made automatic transmissions more competitive with manuals in terms of fuel efficiency, and in some cases, modern automatics outperform manual cars in this area. However, automatic transmission cars usually have a higher purchase price and higher repair costs.
Coasting in Gear vs Neutral
When it comes to coasting in gear or neutral, it is generally more fuel-efficient to coast in gear than in neutral. When coasting in gear, the engine cuts off the fuel supply, while in neutral, the engine requires fuel to keep the vehicle idling. However, in certain scenarios, such as rolling down a large hill and having enough momentum to coast over a smaller hill, it may be more efficient to coast in neutral.
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Frequently asked questions
In the majority of modern cars with electronic fuel injection, a car will not use any fuel when coasting in gear. This is because the computer will detect acceleration without any throttle being applied and will cut fuel to the engine.
When coasting in neutral, a car will use a small amount of fuel to keep the engine idling.
Coasting in gear is generally more fuel-efficient than coasting in neutral. However, there may be some scenarios where coasting in neutral is more efficient, such as when rolling down a large hill and having enough momentum to roll over a smaller hill.
