From
gal (UK)UK Gallon
The UK imperial gallon equals 4.54609 litres exactly. Defined in 1824 as the volume of 10 pounds of water at 62 ยฐF. Still used for fuel economy reporting in the UK and some older industrial contexts. The UK imperial gallon is about 20% larger than the US gallon.
Real-world: UK petrol sold by litre since 1995, but economy is quoted in UK mpg: a diesel car at 60 mpg (UK) uses 4.7 L/100 km.
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