My car did well last month- I've only had to fill her up twice and should run easily till end of this week. Total cost of petrol( gas in the US) was R320($53) for the month. She is an extremely economical car- a Datsun 1200 ' 74 model, that my folks brought new and has always been in the family. I took it over about 4 years ago as the repairs were costing the folks a lot, whereas DH is relatively handy with old cars and our neighbor is a mechanic
DH also gave me the tip of never letting the tank go below a quarter- helps preserve the engine and means you shouldn't run out of fuel.