Fuel and Emissions
Vehicle Idling Emissions Calculator
Estimate direct carbon dioxide produced during accumulated engine idling. Never idle a combustion vehicle in an enclosed space.
Set the calculation inputs
A changed component or operating condition belongs in a new case.
The measurement being modeled
Estimate direct carbon dioxide produced during accumulated engine idling — treat the output as a measured relationship for one operating case.
Never idle a combustion vehicle in an enclosed space — that condition defines when idling co2 emissions is comparable with another result.
For the distinct decision to estimate the economy and fuel-use change associated with a roof rack or rooftop cargo, preserve this answer and open the Roof Rack Fuel Economy Penalty.
Turning the inputs into a result
The Idle fuel rate entry represents fuel consumed during one hour of idling — before calculating, use one clearly defined operating interval rather than combining records from different periods.
Idling time: Total idling time for the selected period — a compatible entry should use one clearly defined operating interval rather than combining records from different periods.
For CO2 per gallon, use the quantity described as tailpipe emission factor for the fuel — in the vehicle record, match the fuel quantity to the same distance, fill method, and operating period.
In “idle CO2 = idle fuel rate × idle hours × CO2 per gallon,” idling co2 emissions follows from the displayed relationship among idle fuel rate, idling time, and co2 per gallon.
No term beyond idle fuel rate, idling time, and co2 per gallon is introduced in “idle CO2 = idle fuel rate × idle hours × CO2 per gallon.”
Following one calculation through
To trace the arithmetic, start with Idle fuel rate = 0.3 gal/hr, Idling time = 90 hr, and CO2 per gallon = 8.887 kg.
After applying the formula, the displayed results are Idling CO2 emissions = 239.9 kg, Fuel consumed while idling = 27.0 gal, and CO2 per idle hour = 2.67 kg/hr.
Using the supporting measurement
Idling CO2 emissions answers “Estimate direct carbon dioxide produced during accumulated engine idling.” The additional displays, Fuel consumed while idling and CO2 per idle hour, are a different view of the same entered measurements.
The calculation excludes cold-start changes and other pollutants — when that condition changes, compare separate calculator runs instead of blending the inputs.
Because never idle a combustion vehicle in an enclosed space, a disagreement between idling co2 emissions and an outside reference should trigger a review of idle fuel rate and co2 per gallon.
Operating conditions outside the formula
The equation cannot determine whether idling time was recorded with a calibrated instrument or under a repeatable operating condition — for idling time, the page specifically expects total idling time for the selected period.
Use the Fuel Tank Range for the separate question of how to estimate usable driving range while retaining a chosen fuel reserve.
Before using this result
What measurement source fits Idle fuel rate when it represents fuel consumed during one hour of idling?
Because idle fuel rate represents fuel consumed during one hour of idling, use a source tied to the exact vehicle, component, and operating period described by the other fields.
How does the warning “Never idle a combustion vehicle in an enclosed space” affect Idling CO2 emissions?
The condition “Never idle a combustion vehicle in an enclosed space” is not corrected automatically by the numeric inputs, so create a separate vehicle idling emissions case when it changes.
What assumption is expressed by “idle CO2 = idle fuel rate × idle hours × CO2 per gallon”?
In “idle CO2 = idle fuel rate × idle hours × CO2 per gallon,” idle fuel rate and idling time are treated as parts of one vehicle case.
How narrowly is Idling time defined by “Total idling time for the selected period”?
The definition “Total idling time for the selected period” excludes a similarly named rating or a measurement taken at another reference point.