How to cut your commuting fuel costs
Updated 23 September 2026
Driving to work is the trip you repeat most, and often the least efficient: short distances, lots of town driving and rush hour. These are the measures that save the most, with what the research says and a worked example.
Why your daily commute uses more fuel
An official fuel economy figure is an average of town, country and motorway driving. Town driving uses more: on US EPA labels, a conventional car’s city fuel use is 9–16% higher than its combined figure. Stops, pull-aways and idling matter far more than on an open-road trip.
On top of that, real-world fuel use is on average 17–20% higher than the official WLTP figure (real-world vs official fuel economy). That’s why it pays to work out your cost with a corrected figure and your commute’s road mix: the commuting fuel cost calculator does both.
Traffic jams and rush hour
Barth and Boriboonsomsin (University of California, Riverside) linked CO₂ emissions, which track fuel use, to real average traffic speed. Compared with normal town driving at around 15 mph:
| Average speed | Fuel per mile | Situation |
|---|---|---|
| ≈ 15 mph (25 km/h) | ×1.00 | Town driving with lights |
| ≈ 11 mph (17 km/h) | ×1.22 | Slow, stop-start traffic |
| 5–7 mph (8–11 km/h) | ×1.7–2.1 | Heavy congestion |
Leaving before or after rush hour, or taking public transport for the most congested stretch, can save more than any driving technique.
Driving style and idling
- Hard acceleration and braking can lower your mpg by 10–40% in stop-and-go traffic and 15–30% at motorway speeds (fueleconomy.gov).
- An idling engine uses a quarter to half a US gallon an hour, about 1–2 litres, depending on the engine and air conditioning (fueleconomy.gov). Stop-start systems avoid most of it at traffic lights.
- Reading the traffic ahead and keeping a steady speed avoids braking that you then have to make up by accelerating.
Air conditioning and weight
Air conditioning uses almost the same amount per hour at any speed (ORNL). On a town commute at 15 mph, that means far more fuel per mile than on the open road: in hot weather, it can add around 2 L/100 km in town to an average car. When opening the windows is better: air conditioning or windows down.
Every extra 100 lb (45 kg) cuts mpg by about 1% (fueleconomy.gov), and more so in town. Empty roof bars or boxes count too: roof boxes and luggage.
What each measure saves: an example
A petrol car rated at 45 mpg (WLTP), 9 miles each way mostly in town, 21 days a month and petrol at £1.40 a litre (example price). With moderate traffic, the month costs £67.
| Scenario | Cost per month | Per person |
|---|---|---|
| Moderate traffic (baseline) | £67 | £67 |
| No traffic jams | £65 | £65 |
| Heavy traffic | £81 | £81 |
| Air conditioning in hot weather | £85 | £85 |
| Sharing with 1 other person | £69 | £35 |
| Sharing with 2 other people | £71 | £24 |
| Working from home 2 days a week (13 days) | £42 | £42 |
The biggest savings come from not making the trip or sharing it: car-sharing between three cuts each person’s cost to a third, and every day working from home saves the whole trip.
Sources
- fueleconomy.gov — Driving More Efficiently
- Barth & Boriboonsomsin (2008), Real-World CO₂ Impacts of Traffic Congestion, TRR 2058
- ORNL — Huff et al., Effects of Air Conditioner Use on Real-World Fuel Economy (SAE 2013-01-0551)
- fueleconomy.gov — Fuel Economy in Hot Weather
- European Commission (2024), COM(2024) 122 — real-world CO₂ emissions