The amount of oil required for car maintenance is mostly not a whole number. Adding 4 or 5 liters of oil is just right, not much, not much, only a few models are whole numbers. Most cars have 3.7-liter, 3.8-liter, 4.5-liter, and so on, with a large bucket of engine oil costing 4 liters and a small bucket costing 1 liter.