Most fleet managers know that manufacturer fuel consumption figures are achieved under controlled laboratory test conditions. Once vehicles enter day-to-day fleet operations, fuel consumption is often significantly higher due to payload, traffic, idling, terrain, driver behaviour and accessory use.
That creates a challenge for organisations trying to estimate their transport emissions. If your vehicles are using more fuel than the official rating, they are also producing more carbon dioxide (CO₂) than the published emissions figure.
Fortunately, there is a simple way to estimate those emissions using data published by the National Transport Commission (NTC).
Fuel consumption and CO₂ emissions are directly linked
Every litre of fuel burned produces a predictable amount of carbon dioxide. Rather than relying on laboratory emissions ratings, fleet managers can estimate real-world emissions by using the vehicle’s actual fuel consumption.
The NTC’s Carbon Dioxide Emissions Intensity for New Australian Light Vehicles 2018 provides a practical reference showing the relationship between fuel consumption and average CO₂ emissions for both petrol and diesel vehicles.
| Fuel Consumption (L/100km) | Petrol (g/km) | Diesel (g/km) |
|---|---|---|
| 3 | 68 | 80 |
| 4 | 91 | 107 |
| 5 | 114 | 134 |
| 6 | 137 | 160 |
| 7 | 160 | 187 |
| 8 | 182 | 214 |
| 9 | 205 | 240 |
| 10 | 228 | 267 |
| 11 | 251 | 294 |
| 12 | 274 | 321 |
| 13 | 297 | 347 |
| 14 | 319 | 374 |
| 15 | 342 | 401 |
| 16 | 365 | 427 |
| 17 | 388 | 454 |
| 18 | 411 | 481 |
| 19 | 433 | 508 |
| 20 | 456 | 534 |
Why this matters
Consider a petrol SUV with an official fuel consumption of 7.0L/100km.
On paper, its emissions would be approximately 160g/km.
However, if telematics or fuel card data shows the vehicle is actually averaging 9.0L/100km, the estimated emissions increase to 205g/km.
Across a fleet travelling millions of kilometres each year, that difference can significantly affect carbon reporting and sustainability targets.
The same applies to diesel vehicles. A diesel ute that consumes 8.0L/100km produces around 214g/km. If real-world consumption increases to 10.0L/100km, emissions rise to approximately 267g/km.
Better fleet data leads to better decisions
Many organisations already collect accurate fuel consumption data through fuel cards, telematics or maintenance systems. Using this information provides a more realistic estimate of fleet emissions than relying solely on manufacturer specifications.
It also helps fleet managers:
- Understand the environmental impact of actual operations.
- Measure improvements from driver training or fuel-efficiency programs.
- Compare vehicle replacement options using real-world operating data.
- Produce more credible sustainability and ESG reporting.
Small improvements deliver measurable benefits
Reducing average fuel consumption by even 1L/100km can produce meaningful reductions in fleet emissions.
For a petrol vehicle, improving from 9L/100km to 8L/100km reduces emissions from approximately 205g/km to 182g/km.
For a diesel vehicle, reducing consumption from 10L/100km to 9L/100km lowers emissions from approximately 267g/km to 240g/km.
When multiplied across hundreds of vehicles and millions of kilometres, these improvements translate into substantial reductions in both fuel costs and greenhouse gas emissions.
A practical tool for Fleet Managers
While official emissions ratings remain useful when selecting new vehicles, actual fuel consumption provides a more accurate picture of a fleet’s environmental performance once vehicles are in service.
Using the NTC fuel consumption and emissions intensity table alongside real-world fuel data gives fleet managers a practical way to estimate CO₂ emissions, benchmark fleet performance and identify opportunities to reduce both operating costs and carbon emissions.
