There is not really any logical preference to either system - some of us grew up with mpg so tend to think in it, but either system works perfectly well, although if your speedo reads in km the metric system is probably easiest. The only logical advantage to mpg over litres/100km is that it is in the form unit/unit rather than unit/100units. As far as I know Australia is the only place this particular unit is used, elsewhere it is km/litre (except for the UK and the US who still officially use imperial units, but the Americans use a wine gallon not an imperial gallon - which maybe says something about the US culture in 1776).

Just to confuse matters my 2a has the dipstick in the right tank in gallons and the dipstick in the left tank in litres!

John

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JDNSW
1986 110 County 3.9 diesel
1970 2a 109 2.25 petrol