You can't directly convert liters of engine oil to kilograms without knowing the oil's density. The density varies depending on the type of oil (e.g., 5W-30, 10W-40) and its temperature. A typical density for engine oil is around 0.85 - 0.9 kg/liter.
Therefore, to find the weight in kilograms, you need to know the volume in liters and the oil's specific density. The calculation would be:
Kilograms = Liters × Density (kg/liter)
