An excess of oil in the engine is harmful for both the engine and the environment.Too high an oil level may cause the engine oil to foam so that its lubricating function is impaired. At the same time increased amounts of oil mist will be carried over into the combustion chambers where they are not completely burned. Besides high oil consumption, unburned oil constituents will be entrained with the exhaust and enter the catalyst converter, where they deposit and will reduce the conversion efficiency in the long term. By routinely checking the engine oil, you can see when and how much to top up. In most engines, the difference between the MAX and MIN marks on the dipstick corresponds to roughly 1 litre. Therefore it is recommended to add 0.5 l at time when the oil level has dropped between medium and minimum.