What is the most fuel efficient speed?

The Energy Saving Trust says that the most efficient speed you can travel in a car in terms of achieving the best fuel economy is 55-65mph. Any faster, though, and the fuel efficiency decreases rapidly. For example, driving at 85mph uses 40% more fuel than at 70mph (oh, and it's illegal too).
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Why is 55 mph the most efficient speed?

The most efficient speed for electric cars is closer to 15-20 mph versus 55 mph for ordinary cars. This is because the losses at low speeds for ordinary cars has to do with the construction and inefficiency of the gas ICE. Directly to the question at hand - they also give the sources of losses over the range of speeds.
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Is it more fuel efficient to go slow or fast?

Slow Down and Drive Conservatively

Speeding increases fuel consumption and decreases fuel economy as a result of tire rolling resistance and air resistance. While vehicles reach optimal fuel economy at different speeds, gas mileage usually decreases rapidly at speeds above 50 miles per hour (mph).
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Which speed consumes less fuel?

Fuel consumption is lowest when driving between 45km/h and 75km/h. Moreover, as a driver, you will have more control over your car and reduce the chance of accidents while driving within this speed range. Fuel consumption can be greatly reduced by accelerating the car gradually and by changing the gear very smoothly.
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Is 70mph fuel efficient?

Fact #982: June 19, 2017 Slow Down to Save Fuel: Fuel Economy Decreases About 14% When Traveling at 70 mph Versus 60 mph. Between 40 and 50 miles per hour (mph) is the optimum cruising speed for high fuel economy in cars and light trucks according to an Oak Ridge National Laboratory study of 74 different vehicles.
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The Most Efficient Driving Speed - An MPG Experiment



Does driving at 60 save fuel?

“We found that limiting your maximum speed to 60 MPH reduces your fuel consumption by 10%,” said Simon East, CEO of DriveGain, “but that this only adds 2 minutes to the average journey time”. “We find drivers tend to over-estimate how much quicker they will arrive when driving faster”, he added.
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Does driving 55 mph saves gas?

You can improve your gas mileage 10 – 15% by driving at 55mph rather than 65mph (104km/h). Natural Resources Canada puts the “sweet spot” for most cars, trucks, and SUVs even lower, between 30 mph (50 km/h) and 50 mph (80 km/h). Note how quickly efficiency drops after 60 mph.
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Does accelerating quickly save fuel?

The harder you accelerate the more fuel you use. In the city, you can use less fuel by easing onto the accelerator pedal gently. To be as fuel-efficient as possible, take 5 seconds to accelerate your vehicle up to 20 kilometres per hour from a stop.
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Does driving slower save fuel?

Going slower technically saves fuel because at high speed your engine needs to work harder to overcome drag from wind resistance, your tyres and transmission, and that drag increases exponentially the faster you go. Reduce your speed, then less power (and thus fuel) needs to be expended to overcome that drag.
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How can I drive to save fuel?

The best advice is to drive as smoothly as possible, gently using the steering, accelerator and brakes. When slowing down, it's important to remain in gear as the fuel cut-off switch in a fuel injection engine is then activated, meaning virtually no fuel is used while braking.
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Does it save gas to not use AC?

Your engine warms up to an efficient temperature faster; summer grades of gasoline can have slightly more energy; and warm air causes less aerodynamic drag than cold air. However, keeping passengers comfortable in hot weather by rolling down the windows or using the air conditioning (AC) can reduce fuel economy.
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Does accelerating quickly hurt engine?

Hard, or rapid, accelerations add stress to the engine and transmission, burning fuel more quickly. When drivers “gun it,” the vehicle sees that as a request for a power boost, burning more fuel than the driver would actually need to reach the same speed more gradually.
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What wastes the most gas in a car?

Driving too fast.

Most American cars operate at peak efficiency—generating the most forward momentum with the least amount of fuel—between 50 and 60 miles per hour.
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Does cruise control save gas?

Generally speaking, yes. Cruise control can help you become more fuel-efficient and can help you save an average of 7-14% on gas thanks to its ability to maintain a continuous speed. In comparison, the constant change in acceleration and deceleration of the driver placing their foot over the pedals can eat more gas.
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Is 55 mph still the most efficient speed?

About 55 miles per hour is the optimum speed for most cars. Kick it up to 65 mph and you are 8 percent less efficient; at 80 mph you are 28 percent less efficient. Slowing down can also mean reducing your carbon footprint.
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How much gas can you save by driving 55?

For every mile per hour faster than 55 mph, fuel economy drops by about 1 percent, said Jason Mark, clean vehicles program director for the Union of Concerned Scientists. The drop-off increases at a greater rate after 65 mph. The faster you go, the faster the fuel goes.
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Do you burn more gas with the AC on?

You might be curious about why your car uses extra fuel when the AC is on. This happens because energy is diverted from the engine to the air conditioner when it's running. This leads to more fuel usage overall. Your car has to get the energy needed to keep your AC running from somewhere.
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Does AC use gas or battery?

When you're taking full advantage of your vehicle's air conditioner on a hot day in San Francisco traffic, you may wonder, does car AC use gas? Yes: The alternator, which is powered by the engine, is what provides energy to the air conditioner. The engine runs on fuel, meaning you are using up gas when you run the AC.
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Why does braking use fuel?

In an engine-braking scenario, the car would carry less speed up to the next hill, so the driver would need to accelerate, using more fuel. Coasting in neutral to gain speed should only be done safely and within applicable speed limits, of course.
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What RPM is an engine most efficient?

Generally speaking, the faster the engine speed, the more fuel the engine is using. Between 1,300 and 1,500 RPM is the most fuel-efficient engine speed, or what some would call the “sweet spot.”
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What wastes fuel in a car?

Braking and accelerating sharply can waste fuel, so consider (as should be done anyway) a sensible, cautious approach to driving which avoids the need for sharp braking. A more consistent approach to your speed will also help to lessen fuel consumption.
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How fast should you accelerate?

Aim to take about five seconds to accelerate your vehicle up to 15 miles per hour from a stop. For a manual transmission, use a moderate throttle position and shift between 2000 and 2500 rpm. One way to help not accelerate too quickly is to imagine there's an egg under the gas pedal.
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What country has no speed limits?

There are only two big places on the map with no speed limit roads: Australia's Northern Territory and Germany. The Northern Territory has gone back and forth on this question: in 2007, it imposed a mandatory speed limit after many years of legal unlimited speeding.
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Is more idling fuel-efficient?

Idling for more than 10 seconds uses more fuel (Figure 3) and emits more CO2 than engine restarting. Idling fuel usage varies from 0.2 to 0.5 gal/h for passenger vehicles across a range of sizes, and increased with idling speed. The vehicle warms up faster when driving than it does when idling.
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How much more fuel is used at 70mph than 50mph?

Explanation: Your vehicle will use less fuel if you avoid heavy acceleration. The higher the engine revs, the more fuel you'll use. Using the same gear, and covering the same distance, a vehicle travelling at 70 mph will use about 15% more fuel than it would at 50 mph.
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