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Engine Idling Fuel Volume & Cost Estimate

Estimate fuel use while stationary from engine displacement and a petrol or diesel coefficient, then calculate cost in the selected units.

  • Formula & worked example
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

The diesel preset estimates 0.45 liters per hour per liter of engine displacement. A 2-liter engine idling for two hours uses 1.8 liters; at 1.50 per liter, the cost is 2.70.

Fuel volume = engine displacement × selected idle coefficient × time; cost = fuel volume × unit price

Worked example

Enter these known values and leave the other values blank.

Illustrative idle-rate preset
Diesel
Engine displacement
2 L
Time spent idling
2:0 hrs / min
Price per selected fuel-volume unit
1.5 USD / L
Estimated idle fuel flow
0.9 L/hr
Estimated fuel volume consumed
1.8 L
Estimated fuel cost
2.7 USD

Assumptions and limitations

  • The captured coefficients are 0.59999976 L/hour per liter of engine displacement for petrol and 0.45 for diesel. These are fixed approximations, not calibrated measurements.
  • The retained engine-size range is above 0.4 and below 15 liters. Duration, fuel price and total use are nonnegative; zero idling time uses no fuel.
  • Real fuel use depends on the vehicle, temperature, accessories and air-conditioning load. Treat the result as a scenario; a measured idle-flow value can also be entered.
  • The price denominator must match the selected liter, US gallon or imperial gallon. Gallon conversions use exact volume definitions.

Common questions

Why can two equally sized engines idle differently?

Displacement alone does not determine fuel use. Engine design, load, ambient temperature and accessories also matter.

Can I use a price per gallon?

Yes. Select the gallon convention on the fuel-price denominator. The result converts fuel volume and price consistently.

References

Bookify requires nonnegative idling duration, consumed fuel and fuel cost, including a valid zero-duration result. Volumetric flow rates use exact US or imperial fluid-volume definitions and exact seconds per minute, hour and day. Bookify replaces the captured rounded US gallon with the exact 3.785411784-liter definition.

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