Question: how far can 1 liter of gas go?
Answer: What qualifies as fuel efficient, then? Anything that is listed as less than 6-litres/100km or more than 16.5km/1-litre is considered to be pretty good. The first (and most common) reference is litres per 100km (litres/100km). This is how many litres of fuel the car needs in order to travel 100km.