Diesel Vehicles
Diesel MPG Calculator
The Diesel MPG Calculator measures the real-world fuel economy of diesel-powered vehicles. Because diesel fuel contains a higher energy density than petrol, diesel engines typically achieve greater thermal efficiency and return higher MPG figures. This makes them a popular choice for long-distance drivers, commuters, and freight vehicles.
You can input your distance traveled and fuel consumed using US gallons, UK (Imperial) gallons, or litres. The calculator automatically computes your vehicle's MPG, standard metric equivalents (L/100km and km/L), and miles per litre, bridging the gap between how fuel is purchased at the pump and how economy is measured.
Diesel combustion produces approximately 2.68 kg of CO₂ per litre of fuel burned (compared to 2.35 kg for petrol). Although diesel vehicles are generally more fuel-efficient, they also emit higher levels of nitrogen oxides (NOx) and particulate matter. This calculator provides estimates for both fuel costs per mile and total carbon dioxide emissions per tank to help you monitor your vehicle's economic and environmental performance.
How to Use
- Enter the miles driven.
- Choose your fuel unit: US gallons, UK gallons, or litres.
- Enter the diesel used.
- Optionally add the diesel price per unit.
- Click Calculate Diesel MPG (or press Enter).
Related tools: MPG Calculator, Petrol MPG Calculator, UK MPG Calculator, Miles Per Litre Calculator.
Got Questions?
Diesel MPG Calculator FAQ
Yes, diesel engines typically achieve 25–30% better fuel economy by energy content. A diesel car that gets 55 MPG might only get 42 MPG on petrol. However, diesel fuel costs more per litre in most markets.
Same method as any MPG: miles driven ÷ gallons used. The fuel type doesn’t change the formula — only the CO₂ output per gallon differs.
In UK figures, 55–70 MPG is excellent for a diesel. Most modern diesel cars achieve 50–65 MPG on the WLTP cycle, with real-world figures 10–15% lower.
Diesel produces approximately 2.68 kg of CO₂ per litre burned. For a car doing 55 UK MPG (5.14 L/100km), that’s about 138g CO₂/km — slightly above the EU average target.
Many countries including the UK plan to ban new diesel and petrol car sales by 2035. Existing diesel cars will remain road-legal for many years beyond that date.