Making use of the MDS, the engine helps to improve fuel economy when operating at steady speeds, while accelerating slowly or traveling up a small incline. MDS engines are able to use standard roller tappets, but use deactivating roller tappets in cylinders 1, 4, 6 and 7, as indicated by the two holes on the side for the latching pins. You should always fit the guide holder and tappets together and in their normal position for a safe engine. Lubrication should always begin with the tappet guide holder and tappets. In case you are recycling the tappets and guide holder assembly, put them back in their exact position. After that, place the tappet guide holder and tappets on the engine and tighten the retaining bolt to 12 Nm (9 ft. lbs.). After that, fit the cylinder head and then attach the negative cable to the battery. To ensure the valve assembly is safe, run the engine at fast idle only after all of the lash adjusters are lubricated and have fallen silent. After that, fire up the engine, look for any signs of fluid leaking and test the vehicle for 15 minutes on the road.