If petrol costs 90p a liter how many liters would i need to make a gallon?

If petrol costs 90p a liter how many liters would i need to make a gallon?
The cost of petrol is irrelevant to the number of litres in a gallon which is approximately 4.5. Therefore the cost of a gallon of petrol at 90p per litre is 3.60. Furthermore if petrol costs 90p per litre you should fill the tank and a couple of jerry cans, not just buy a litre!