Optimal Speed for Fuel Efficiency

In summary, the best speed for fuel economy varies depending on factors such as engine load, RPM, and air resistance. For a car, the most efficient speed is the lowest speed it can comfortably hold in its highest gear. However, it also depends on your driving style and the specific car you are using. Generally, going too slow or too fast can decrease fuel efficiency.
  • #1
nuclear-boy
33
0
hi,



what is the exact best speed for fuel economy?

why is 5mph less economic than 75mph?
 
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  • #2
33.7 mph is best
 
  • #3
seriously, it is god that you asked this question .. we need a little more information ..it is like you ask..How high is the sky?
whats the best speed for mpg economy for a bus?
automobile? train. plane? truck...
in the desert on dirt roads or highway with unlimited sped limits..in restrictive epa mandated smog dictatorship like California or wide open spaces where no emission equipment is required..like Daytona ??
 
  • #4
For a car the most efficient constant speed is the lowest speed it can comfortably hold in its highest gear.
 
  • #5
As for me using 1NZ-FE VVT-i, u pumped about 15 liters (approx 4 gallons) I can traveling about 250 km (155 miles) at speed 100 kmh (60 mph). Actually, it depends on your driving style too.
 
  • #6
I agree with Russ. The internal combustion engine is most efficient at ~35% of redline and 80% of maximum torque, as shown in BSFC (brake specific fuel consumption). See thumbnail. For lower power requirements, the engine RPM should be reduced by staying in the highest gear to maintain high torque.

[added] Note in the thumbnail that the lines of constant power in the BSFC map are hyperbolas. If you shift gears without changing velocity, you move along the hyperbola.

Bob S
 

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  • #7
nuclear-boy said:
hi,

what is the exact best speed for fuel economy?

why is 5mph less economic than 75mph?

At 5mph the engine is using more energy to simply keep itself spinning than it is to move the car.

Other than that, it depends on many factors. If you go too slow, your engine will not be at its most efficient point. As has been mentioned, an engine is most efficient at a particular load and a particular rpm.

Engines are also most efficient at wide-open-throttle. Just that fact itself means you have to be going at a decent speed.

At the other end of the spectrum, the faster you go, the more air resistance (it goes up with your speed squared), so the more energy gets wasted due to friction.

All these factors and more determine which speed is best for fuel economy. It will be different for every car.
 
  • #8
thanks for all of your help, i greatly appreciate it :)
 

What is the best speed for fuel economy?

The best speed for fuel economy varies depending on the vehicle and driving conditions. Generally, driving at a consistent speed between 40-60 mph can result in the best fuel efficiency.

How does speed affect fuel economy?

As speed increases, air resistance and drag also increase, causing the engine to work harder and use more fuel. This means that higher speeds typically result in lower fuel economy.

Is it better to drive at a constant speed or vary your speed for better fuel economy?

Driving at a consistent speed can help improve fuel economy, as frequent acceleration and deceleration can use more fuel. However, in certain driving conditions, such as in heavy traffic, varying your speed may be necessary.

Does the type of vehicle affect the best speed for fuel economy?

Yes, the type of vehicle can greatly impact the best speed for fuel economy. Generally, smaller and more aerodynamic vehicles will have a higher optimal speed for fuel efficiency compared to larger and less aerodynamic vehicles.

Are there any other factors besides speed that can affect fuel economy?

Yes, other factors such as tire pressure, vehicle maintenance, and driving habits can also impact fuel economy. It is important to regularly maintain your vehicle and practice efficient driving techniques, such as avoiding sudden accelerations and maintaining a steady speed.

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