It all depends how it is driven there are some three cylinder petrol engines and small 4 cylinder engines that can go down to 40mg i have had that experience and a bigger engine you do not need to wring the life out of it.Some Pure electric cars people are finding that if not used and plugged in at home the batteries are draining and there maybe only 8 to 10 mile charge left with a combustion engine we know the batteries can can lose charge over time but it can be remedied in charging it or replacing it cheaply this is on a you tube usa video so are we sure that it is cheaper depending on use to have a large engine used euro 6 motorway speed 65 to 70m that gives 40 or more mpg that is not bad only that in usa super unleaded is only over $4 and here and europe they are trying to force us into electric cars.