Gallons per 100 miles (UK) to Liters per km

Fleet managers and logistics companies in the UK sometimes prefer this consumption-based metric because it scales linearly with cost. If fuel costs £5.50 per imperial gallon, a vehicle using 3 gal/100mi costs exactly £16.50 per 100 miles — much easier to budget than working backwards from mpg.

UK gal/100mi values are about 17% lower than US gal/100mi because the imperial gallon is larger. A car consuming 4 US gal/100mi uses only about 3.33 UK gal/100mi. Same fuel burned, but fewer of the bigger gallons needed to measure it.

Burning one imperial gallon of diesel produces about 10.2 kg of CO₂. Multiplying gal/100mi by that emission factor gives a direct kg-CO₂-per-100-miles figure for each vehicle. Fleet managers set thresholds — say 25 kg CO₂/100mi — and flag any vehicle exceeding it for maintenance or driver retraining. The linear relationship makes gal/100mi far better than mpg for carbon accounting, where small absolute savings matter.

A modern family hatchback should achieve around 1.8–2.3 UK gal/100mi (43–56 UK mpg). Anything under 2 gal/100mi is considered very efficient. SUVs typically sit at 2.5–3.5 gal/100mi, and performance cars can exceed 4 gal/100mi.

Not on consumer-facing documents. UK vehicle registration (V5C) and type-approval certificates show L/100km and CO₂ g/km. Gal/100mi (imperial) lives mainly in fleet management software, academic transport research, and engineering reports where linear consumption comparisons matter more than the traditional mpg framing.

L/km is the raw mathematical unit that telematics systems and engine control units log internally. It maps directly to instantaneous fuel flow divided by speed, making it ideal for real-time calculations. Multiplying by 100 to get L/100km is a display convenience for humans, not a computing necessity.

Modern telematics units sample fuel flow and GPS speed several times per second, computing instantaneous L/km continuously. When the value spikes — hard acceleration, excessive idling, speeding — the system triggers an in-cab alert or scores the behavior for later review. Over thousands of vehicles, coaching drivers to shave even 0.005 L/km off their average can save a fleet millions of liters per year.

An F1 car burns roughly 0.35–0.45 L/km under race conditions, about five times more than a typical passenger car. FIA regulations cap total fuel at 110 kg per race, forcing teams to balance speed against consumption strategically.

Yes, 0.05 L/km (equivalent to 5 L/100km or ~47 US mpg) is quite efficient. Most petrol hybrids achieve this range. A non-hybrid petrol car would need to be a well-optimized compact to hit that mark consistently in mixed driving.

OBD-II standardized on raw per-kilometer (or per-mile) metrics because the ECU calculates consumption at the granular level. Your dashboard or app multiplies by 100 for display. The raw L/km reading updates in real time and is more useful for diagnosing injector performance or driving behavior.