What is Fuel consumption: Definition and 39 Discussions

Fuel efficiency is a form of thermal efficiency, meaning the ratio of effort to result of a process that converts chemical potential energy contained in a carrier (fuel) into kinetic energy or work. Overall fuel efficiency may vary per device, which in turn may vary per application, and this spectrum of variance is often illustrated as a continuous energy profile. Non-transportation applications, such as industry, benefit from increased fuel efficiency, especially fossil fuel power plants or industries dealing with combustion, such as ammonia production during the Haber process.
In the context of transport, fuel economy is the energy efficiency of a particular vehicle, given as a ratio of distance traveled per unit of fuel consumed. It is dependent on several factors including engine efficiency, transmission design, and tire design. In most countries, using the metric system, fuel economy is stated as "fuel consumption" in liters per 100 kilometers (L/100 km) or kilometers per liter (km/L or kmpl). In a number of countries still using other systems, fuel economy is expressed in miles per gallon (mpg), for example in the US and usually also in the UK (imperial gallon); there is sometimes confusion as the imperial gallon is 20% larger than the US gallon so that mpg values are not directly comparable. Traditionally, litres per mil were used in Norway and Sweden, but both have aligned to the EU standard of L/100 km. Fuel consumption is a more accurate measure of a vehicle's performance because it is a linear relationship while fuel economy leads to distortions in efficiency improvements.
Weight-specific efficiency (efficiency per unit weight) may be stated for freight, and passenger-specific efficiency (vehicle efficiency per passenger) for passenger vehicles.

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  1. W

    I Effect of moving cargo on vehicle fuel consumption

    I have to calculate how much fuel is wasted, when you do not fix a load in a vehicle. So lets say there is a heavy box sitting in an almost empty truck. If this box moves how much fuel is lost? Or if you fix the box, how much fuel do you save?
  2. J

    I Does Pulse and Glide only work with manual transmissions and a kill switch?

    When car drive uphill, gravity/weight has drag component, that is reason why you must add more throttle compare to ligther car at same constant speed uphill. So logicaly car increase fuel consumption. But if you drive downhill, gravity/weight has thrust component, so your top speed("terminal...
  3. J

    I Car drag coefficent vs fuel consumption link

    Car has drag coeffecient of 0.35 and drink 5L/100km, if car Cd is reduced to 0.20 and everthying else stay the same(frontal area,power,weight etc),how much will car drink? Is it possible to calcualte this or we need something more? I am interested if exist direct link/formula between Cd and...
  4. PainterGuy

    B Time dilation, relativistic mass and fuel consumption

    Hi, Could you please help me with the queries below? Question 1: A GPS satellite is moving faster than the earth, for every day on Earth the clock on the satellite shows one day minus 7 microseconds due to time dilation due to special relativity. However, since the Earth's gravitational pull...
  5. parazit

    Mass of the fuel consumed at the reactor each year?

    Hi fellows. I am dealing with the following question and any help to solve it will be a huge favor. Let us consider a nuclear power plant which delivers 100 MWe. The plant is based on a Rankine cycle, where the steam exiting the reactor is at 350 C and water exits the condenser at 20 C. The...
  6. joker1319

    Automotive "Engine fuel consumption map" without the torque possible?

    Hello, I am currently facing a problem. I'm on a project and trying to create an "engine fuel consumption map (engine torque / engine speed)" among other things. Unfortunately, the engine torque is not measured in my measurements. More specifically, the "actual engine - percent torque (OBD PID...
  7. mastermechanic

    Why Is My Porsche 911 Fuel Consumption Calculation So Different?

    I was looking at the technical specs of Porsche 911. It has 427 kW power and 7.5 liters/100 km fuel consumption on highway. I made a quick calculation but I got strange result. Please tell me why ; First I assumed that the car has 90 km/h constant speed on highway so it will take 1.11 hours to...
  8. D

    Why Does My Car's Fuel Gauge Show False Readings on Hills?

    hello i am new here. I am facing a problem in fuel gauge that when i drive for a long time on hills it start to show false value. I decided to solve this problem i have a gyro and known resistance from fuel tank of my car and now i want to have true value all the time please help me with it or...
  9. dean barry

    What factors affect fuel consumption and speed in road vehicles?

    I was wondering about the amount of fuel used for a given journey. My model is that the same journey is made at two different constant speeds I have assumed that instantaneous fuel consumption is proportional to the power produced by the engine at that point. I an ignoring rolling resistance...
  10. M

    Burner and fuel consumption rate

    I don't know how to determine the fuel consumption rate of a gas burner and would like to seek for help. Also, is there any relationship between the number of rings of gas burner and the fuel consumption rate?
  11. 0

    Calculating Fuel Consumption for a Boiler at 2.1 MN/m2 Pressure

    Homework Statement A boiler is to produce 6250 kg/h of steam superheated by 40 oC at a pressure of 2.1 MN/m2. The temperature of the feedwater is 50 oC. If the thermal efficiency of the boiler is 70%, how much fuel oil will be consumed in one hour? The calorific value of the fuel oil used is...
  12. G

    Determining the acceleration of an aircraft

    Hello everyone. I'm currently doing a research on aircraft performance for my school project, which require me to design an airfoil to suit a specific mission. I'm not very familiar with the formulas used for calculating the aircraft performance and I would like to seek help from the forum...
  13. Goldisach

    How to find Fuel consumption for 10 MW Gas Generator

    Hi I am working on Bio Gas Project and I want to know calculations/Formulas to find out elements of Generator. I am MBA students and i have to submit my project report with to start up new firm on renewable energy. Please submit can share your knowledge to help me.
  14. A

    How does a car's loads affect it's fuel consumption?

    Hi, so I was wondering about how the car's LED, MP3/IPOD, AC systems consumes up electrical power and then to fuel? Let's say that the loads are running for 5-7 hours. Thanks for the replies/ideas!
  15. Prashan Shan

    What will be the rate of fuel consumption of a rocket near 'c'

    when an object moves relative to something it experiences time at a slower rate right? now let's assume that an rocket moves 99.99% the speed of light, then what will be the rate of fuel consumption? will it remain the same or it will increase/decrease?
  16. Hunter Bliss

    Calculus of Variations: Minimizing Fuel Consumption w/ v(t)

    Homework Statement (I'm learning all of this in German, so I apologize if something is translated incorrectly.) So last week we started calculus of variations, and I'm rather confused about how to approach the following problem: The fuel consumption of a vehicle per unit of time is expressed...
  17. R

    Speed/Distance/Time + Fuel Consumption

    Homework Statement Distance = Speed / Time Speed = Distance / Time Distance = Speed * Time Also breaking up "chunks of time" in an hour 2 of 30 mins 3 of 20 mins 4 of 15 mins 5 of 12 mins 10 of 6 mins 12 of 5 mins 15 of 4 mins 20 of 3 mins 30 of 2 mins Homework Equations 1) An example of an...
  18. M

    What Affects Generator Load and Fuel Consumption?

    What I know is there 2 friction; Air resistance and Weight of rotor? Is load of generator consider as friction? I noticed that when generator's load is half, fuel consumption is reduced (but RPM and frequency is still same). I tried to think how that, although weight of rotor is constant. does...
  19. N

    Minimum Rate of Rocket Fuel Consumption

    Homework Statement A rocket which has an exhaust speed of 8.0 km/s is to have a vertical acceleration of 8.0 m/s2. If the initial mass of the rocket is 6.0x106 kg, at what minimum rate must the rocket consume fuel? Homework Equations F = ma F = RVREL The Attempt at a Solution F...
  20. R

    Rocket thrust, mass, speed given initial m and fuel consumption rate?

    A rocket, which is in deep space and initially at rest relative to an inertial reference frame, has a mass of 59.5E5 kg, of which 7.39E5 kg is fuel. The rocket engine is then fired for 300 s, during which fuel is consumed at the rate of 480 kg/s. The speed of the exhaust products relative to the...
  21. C

    Fuel consumption increases during winter?

    I guess that if the answer is "yes" then the difference will be neglectable, but anyway... I was wondering if during winter, fuel is less efficient than summer. During summer, there is some extra energy content in the fuel, due to increased temperature. This extra energy is added to the energy...
  22. A

    Equation of non-symmetric cone for fuel consumption maps

    Dear Brains I am working on fuel consumption maps to be included in vehicle simulation software to calculate the fuel consumption. To be able to create the map you need 3 things : RPM, Engine Power, and consumption (kgr/h) or efficiency of the engine (Depending on the consumption). You take...
  23. smokingwheels

    Is reducing an engines fuel consumption by 85% impossible?

    I expect to be shot down in flames but I don't mine one bit. I have just done a bit of a drive in my 28 year old Nissan Bluebird Wagon about 10% city 90% HWY...NO Fancy EFI systems or direct injection here just a plain old carburetor running slightly rich at idle. I just did a rough...
  24. C

    Boiler efficiency and fuel consumption

    Homework Statement A boiler is to produce 6250 kg/h of steam superheated by 40 oC at a pressure of 2.1 MN/m2. The temperature of the feedwater is 50 oC. If the thermal efficiency of the boiler is 70%, how much fuel oil will be consumed in one hour? The calorific value of the fuel oil used is...
  25. M

    Why is fuel consumption higher at low RPM?

    Why are usually more wasteful fuel engine at low RPM, as the example image below, 900 RPM more wasteful fuel consumption than 1600 RPM.
  26. C

    Calculating aircraft fuel consumption

    I'm doing some research into advances in aircraft and need to calculate some (rough) values for aircraft consumption per passenger. The only method I can think of is calculating the maximum fuel weight at maximum payload (Maximum Take Off Weight (MTOW) - Maximum Zero Fuel Weight (MZFW)) and...
  27. A

    Optimization of fuel consumption question

    Homework Statement The fuel consumption of a river boat is kv3 litres per hour where k is a constant and v km/h is it's speed through the water throughout this question v > 4 km/h. i) determine the fuel consumption for a trip of x km against a current of 4km/h and find the speed at which...
  28. J

    Gear mechanism and wheel arrangement for reduction of fuel consumption

    Hi everyone, I hope I have posted in the right place. I'm a commerce student and have absolutely no idea about mechanical stuffs. My father has an idea in mind which he would love to implement. He too is a commerce student. Hence, I need some help from you'll to see if this is really practical...
  29. G

    Fuel Consumption of a Ship Traveling at Near Light Speed

    Imagine this scenario: An "airplane" that runs on some type of fuel, let's say, liquid, reaches 90% of the speed of light. Once it achieves this speed, will the ship require less fuel due to time dilation, the same amount of fuel due to time dilation, or more fuel to maintain a constant...
  30. M

    Calculating Friction Power from Fuel Consumption Graph

    how do we calculate friction power from the graph of total fuel consumption versus brake power?
  31. M

    Fuel consumption more in 2stroke?

    is it true that fuel efficiency is better in a 4stroke engine ? since the number of strokes are more in case of a 4stroke engine,the energy required would be more ,right?
  32. S

    Engine size/type (ie. 2L inline-4) and fuel consumption

    Hi everyone, new poster here. :) Came across this forum the other day and found quite a few nice topics that were interesting and the people sounded like they knew their stuff ... so i joined. Now the question... I am interested in fuel efficiency as regards the engine capacity. For...
  33. S

    Rocket fuel consumption too easy?

    Homework Statement Rocket with fuel mass of m(initial) Rocket without fuel is m(final) Time for fuel to be used up is t(final) Homework Equations What is m(t) (slope of m vs t graph) (i assume t(initial) is zero The Attempt at a Solution [((m(final) -m(initial)) / t(final)]t +...
  34. M

    Matter-antimatter ship in GR clock paradox - fuel consumption

    hi, recall the familiar round trip - it's more or less the same as in this arXiv article (http://arxiv.org/PS_cache/physics/pdf/0604/0604025v3.pdf) - round trip with acceleration g. me and my friends were wondering the following: imagine that the passenger abroad the rocket travels for 4...
  35. I

    Rocket Fuel Consumption: Calculation of 80kN Takeoff Rate

    The weight of a rocket is 80kN at the instant it takes off , and the products of the combusion are ejected at a velocity of 0.60 kms-1 relative to the rocket. Calculate the rate at which the rocket must be consuming fuel in order to take off vertically. Ans: 134kgs-1 Cant find a solution...
  36. S

    What is the Fuel Consumption of a Motor After 7 Minutes?

    Homework Statement I posted int he other section but not sure if that area was a bit high maths I have this questions an answer to it would be great. .Q.1 At t minutes after an engine starts, the rate of fuel consumption is Rkg per minute. it is given by R=10+ 10/2t+1. a) Sketch R as...
  37. C

    Maximizing Vertical Lift: VTOL Engine Designs in Fighter Jets

    Greetings! Would anyone know about how much fuel does a Harrier aircraft (with the Pegasus Turbo fan engine) consume when taking off verticaly? I tried searching the net with no success. Thank You Chris
  38. A

    Calculate Fuel Consumption for Cars: Tips & Advice

    Hi, Does anybody know how to calculate the fuel consumption of a car? Any help would be great Thanks Alex
  39. Nebula

    Relativity and fuel consumption

    I've got a little question here. Basically we've got this guy named "B" driving a straight track with a high constant velocity u. His buddy, "C" on the side of the track measures B's fuel consumption to be dn/dt. Now C filled the tank with just enough gas to make it the distance of the track...