- 8,725
I dont know were your mom gets her figures from but a gallon here in the UK is 4.54609 litre. very near to the US measure above.
Oh, yeah, it's only about three quarters of a litre out - that's about a pint and a third. Or 20%; a fifth, like VAT, or (basic) income tax. We barely notice that.
Fuel efficiency figures are very near identical, for small numbers. Still a 20% difference, mind.