At the pump, how much CO2 are you really paying for?
Every week, millions of French people fill up their cars without thinking about anything other than the price at the pump. Yet behind every liter of gasoline or diesel lies a precise amount of CO2 released into the atmosphere. Understanding this figure is the first step toward becoming aware of the carbon footprint of your mobility — and toward exploring alternatives.
The basic numbers: CO2 per liter of fuel
Burning fossil fuels produces CO2 in a predictable and quantifiable way. The chemical equations don't lie:
- Gasoline (SP95, SP98, E10): approximately 2.28 kg of CO2 per liter consumed.
- Diesel: approximately 2.65 kg of CO2 per liter consumed.
- LPG (Liquefied Petroleum Gas): approximately 1.63 kg of CO2 per liter consumed.
- E85 (flex-fuel ethanol): approximately 1.11 kg of CO2 per liter consumed (accounting for CO2 absorbed by crops).
These figures correspond to so-called "tailpipe" or "tank-to-wheel" emissions. If we include emissions from oil extraction and refining ("well-to-wheel" cycle), the numbers increase by approximately 20 to 25%.
Let's calculate: the footprint of a standard fill-up
A standard car fuel tank holds between 40 and 70 liters. Let's take the example of an average driver:
- 50-liter gasoline fill-up: 50 x 2.28 = 114 kg of CO2, or 0.114 tonnes.
- 50-liter diesel fill-up: 50 x 2.65 = 132.5 kg of CO2, or 0.133 tonnes.
The average French driver covers approximately 13,000 km per year. With an average consumption of 7 liters per 100 km, that represents 910 liters per year, meaning:
- On gasoline: 2,075 kg of CO2, or more than 2 tonnes per year, from driving alone.
- On diesel: 2,411 kg of CO2 per year.
Remember that the Paris Agreement target is to get down to 2 tonnes of CO2 total per person per year by 2050. Driving alone already consumes the entire budget.
Gasoline vs. diesel: the carbon match
Diesel produces more CO2 per liter than gasoline, but diesel engines generally consume less fuel for the same trip. The final result therefore depends on the vehicle's actual consumption.
In practice, for an equivalent vehicle:
- A gasoline model consumes approximately 7 to 8 L/100 km, producing 160-182 kg CO2/100 km.
- An equivalent diesel model consumes approximately 5.5 to 6.5 L/100 km, producing 146-172 kg CO2/100 km.
The CO2 advantage of diesel is therefore slim — about 5 to 10% less per 100 km — and does not by itself justify choosing diesel, especially given the much higher emissions of fine particles and nitrogen oxides, which are harmful to public health.
What about E85 flex-fuel ethanol?
E85 is composed of 85% bioethanol produced mainly from sugar beets and cereals in France. Its carbon footprint is significantly better than regular gasoline: approximately 50% fewer emissions over the entire lifecycle. A 50-liter E85 fill-up emits about 55 to 60 kg of CO2 equivalent — compared to 114 kg for gasoline.
An important caveat: crops dedicated to biofuel production have their own environmental impact (land use, fertilizers, water). The real picture is therefore less ideal than the raw numbers suggest.
How to calculate your car's carbon footprint
The most accurate calculation method uses your vehicle's actual consumption, which you can read from your dashboard or estimate from your fuel expenses:
- Record the number of liters consumed over a period (for example, over a year using your receipts or your banking app).
- Multiply by the emission factor for your fuel (2.28 for gasoline, 2.65 for diesel).
- Add approximately 20% to include upstream emissions (extraction, transportation, refining).
To go further and calculate your entire personal carbon footprint, check out our guide on how to calculate your personal carbon footprint.
Does the electric car really change the game?
In use, an electric car charged on the French grid (one of the most decarbonized electricity mixes in Europe thanks to nuclear power) emits approximately 0.4 to 0.7 kg of CO2 per 100 km — that's 20 to 40 times less than a combustion-engine vehicle. Over 13,000 km per year, that represents 52 to 91 kg of CO2, compared to 2 tonnes for gasoline.
The difference is dramatic in everyday use. Manufacturing the battery does generate additional emissions (7 to 15 tonnes depending on size), but the carbon breakeven point is generally reached between 30,000 and 60,000 km, or 2 to 4 years of use for an average driver.
For a complete lifecycle carbon footprint comparison, our article combustion vs. electric car: the real carbon footprint compared goes into all the details.
Alternatives for reducing your road carbon footprint
While waiting to change vehicles, several levers can significantly reduce the emissions of your combustion-engine car:
- Eco-driving: anticipate braking, maintain a steady speed, avoid sudden acceleration. Smooth driving can reduce fuel consumption by 15 to 20%.
- Carpooling: sharing a trip between two people cuts per-passenger emissions in half. Platforms like BlaBlaCar or Karos for commuting make this easy.
- Tire pressure: underinflated tires increase consumption by 2 to 4%. A small detail, but easy to fix.
- Speed reduction: dropping from 130 to 110 km/h on the highway reduces fuel consumption by about 20%.
- Regular maintenance: clean air filter, proper engine oil, spark plugs in good condition — all of this affects consumption.
"In France, transportation accounts for 31% of greenhouse gas emissions, of which 54% are attributable to private cars. It is the sector where the French have the most individual room for action."
— ADEME, Key Transport Figures 2024
What about offsetting the CO2 from your trips?
For the emissions you can't yet reduce — essential daily commutes, business travel — carbon offsetting offers a credible alternative. The cost of offsetting one tonne of CO2 through certified projects ranges from 15 to 40 euros. For an average driver emitting 2 tonnes per year through their car, that represents 30 to 80 euros per year — a reasonable amount to neutralize your driving footprint.
Apps now make it possible to do this automatically, by calculating emissions from your bank transactions at the pump and automatically deducting the corresponding contribution. This is precisely the approach OFFSET explores, by connecting your actual spending to certified offset projects.
Awareness starts with the numbers. And now, you have yours.