The problem: Every year a car is driven so the internal parts of the engine are wearing away. None more so than the piston rings and cylinder walls. As metal wears so the respective parts no longer match together. This leaves gaps between valve stems and valve guides as well as oil rings and cylinder walls. Oil is sucked down past valve guides and allowed to pass by oil rings into the combustion chamber. During the combustion cycle the excess of oil is burnt causing black smoke and pollution from the exhaust. The action: The addition of Bardahl No Smoke increases the viscosity of standard oil at normal operating temperatures. A 15w40 multigrade becomes the equivalent of 15w60 then suitable for old and worn engines. The added viscosity at high temperature means that the oil is no longer allowed to pass into the combustion chamber and be burnt in the combustion cycle. It is not possible for a standard grade oil to do this without being ‘fortified’ with Bardahl No Smoke.