Classic oil is used mainly in older classic vehicles that don’t require a multigrade oil specification, or any added detergents. It is also used on some lawn mowers and smaller marine diesel engines. Classic oil is not suitable for modern petrol or diesel car engines, so check your handbook to ensure you get the correct oil grade for your car. A mono grade oil, like SAE 30 or SAE40 is suitable for use as lawn mower oil, but will not provide the correct lubrication for a modern engine.