Castrol MAGNATEC 10W-40 A3/B4 is suitable for use in Automotive gasoline and diesel engines where the manufacturer recommends an API SL/CF, ACEA A3/B4, A3/B3 or earlier specification 10W-40 lubricant. Up to 75% of engine wear happens while your engine warms up. When the engine stops oil drains off critical engine parts, however Castrol Magnatecs intelligent molecules dont. They cling to the engine like a magnet providing an extra layer of protection. Castrol Magnatecs unique formulation protects from the moment you turn the key, dramatically reducing engine wear. Now with ultra-refined molecules, for protection you can see, hear and feel. Castrol Magnatec. Instant protection from the moment you turn the key.