1 gallon of oil gives you how many gallons of gasoline?

Answer:

So, roughly, one gallon of crude oil gives you half a gallon of gasoline.
So it takes two gallons of crude oil to produce one gallon of gasoline.

The same ratio applies to litres

So, roughly, one litre of crude oil gives you half a litre of petrol.
So it takes two litres of crude oil to produce one litre of petrol.

See the linked questions below.

2 gallons of oil make about 1 gallon of gasoline. The remainder goes into jet fuel, lubricants, and other petroleum-based products.